When September’s Full Harvest Moon rises above the horizon Friday evening, it will be the final big, bright Super Moon of the year — and the last for nearly another calendar year. As the leaves begin to change and the nights begin to cool off, here’s what you’ll see when you step outside and why.
What is a Super Moon?
Super Moon is the unofficial term for a Full Moon that occurs near perigee, the closest point to Earth in the Moon’s orbit around our planet. Because our satellite’s orbit is not completely circular, it approaches slightly closer and subsequently swings slightly farther out throughout its 27.3-day orbit.
The lunar month — the time it takes for the Moon to go from New to Full to New again, is slightly longer than its orbit: 29.5 days. Because these two periods are not quite the same, they don’t always line up. But sometimes they do, resulting in a Full Moon that occurs when the Moon is closest (or nearly closest) to Earth. We call that a Super Moon.
The details on September’s Super Moon
Astronomers consider a Super Moon to be a Full Moon that occurs when the Moon’s distance is 90 percent or more of the distance from its farthest point, apogee, to its closest point, perigee.
This month, the Moon reaches perigee this evening at 8:59 P.M. EDT, when it will sit 223,269 miles (359,317 kilometers) away. Less than 12 hours later, Full Moon occurs at 5:58 A.M. EDT Friday morning, when our satellite is 224,658 miles (361,552 km) from Earth, or within about 96 percent of perigee, according to Fred Espenak’s AstroPixels page. At that time, our satellite will appear some 33.1′ across in the sky, slightly larger than its average size of 31′.
Seeing the Super Moon
Early risers on Friday can catch the Moon sinking toward the western horizon in the growing dawn, setting shortly after sunrise. But truly the best time to observe the Super Moon is beginning shortly after moonrise, which occurs roughly around the time of sunset during the Full phase. When Full, the Moon is visible from sunset to sunrise, so whether you’re able to look up right after sunset, catch the Moon in the nighttime sky, or see it early in the morning before dawn, you’ll still get a chance to observe the Super Moon.
Below are the times for sunrise and sunset on Friday, September 29, in local time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. local time from the same location.
Although a Super Moon is slightly larger in the sky than average, the difference in size is not something the naked eye can pick up. However, astrophotographers often compare images of the Super Moon to those taken when Full Moon occurs at apogee, or the farthest point from Earth. The size difference between these two occurrences can be up to 14 percent.
Similarly, it’s difficult for the human eye to pick up the difference in brightness between an average Full Moon and a Super Moon; nonetheless, many people do notice the Full Moon appears slightly brighter when it is closer to Earth. This Friday, the Full Moon will appear just over 1 percent brighter than it does on average.
The last Super Moon of 2023
This year, we’ve been treated to a total of four Super Moons: one in July, two in August, and this week’s in September. After this month, the next Super Moon won’t occur until August 2024 — and according to Espenak’s page, it will be the first of a similar succession of four Super Moons, running from August through November.
Although Super Moons may not appear noticeably huge or blindingly bright to the eye, they’re still an excellent excuse to get out under the nighttime skies and observe or photograph Earth’s only satellite. The editors at Astronomy would love to see and share your Super Moon shots — you can send them to us by emailing TIFF or JPG files to readergallery@astronomy.com.
The James Webb Space Telescope (JWST) has detected the earliest and most direct signature for carbon-rich dust grains from the early universe. Experts had previously thought that elements heavier than hydrogen and helium were signatures of older galaxies. But the presence of carbon in young galaxies suggests otherwise, and challenges current theories about dust formation.
A study published in Nature this July offers vital clues about cosmic dust and its role in galaxy evolution in the first billion years of cosmic time. Cosmic dust grains can range in size from just a few molecules to 0.004 inch (0.1 mm) and can vary greatly in composition. After mostly forming in stars, dust is thrown into space by various events, like winds or supernovae.
Dusty space
Dust-filled areas can make observing a challenge because it absorbs light. Fortunately, depending on the chemical composition of the dust molecules, different elements absorb light at different, specific wavelengths. By noting the wavelengths of light that are blocked, astronomers can essentially reveal what the dust is made of.
Using this technique and data from JWST, researchers at the University of Cambridge were able to detect carbon-rich dust grains one billion years after the universe came to exist. Observations of the local, modern-day universe often find these two same carbon-based molecules: polycyclic aromatic hydrocarbons (PAHs) and microscopic graphites. However, astronomers have long thought that these molecules should not exist in the distant, early universe because they wouldn’t have had time to form. Models have suggested it would take hundreds of millions of years to form PAHs.
Making star stuff
Detecting this carbon-rich dust in the early universe is changing how experts understand the cosmos. Researchers are now hypothesizing about what could have created it so soon after the Big Bang.
Alternatively, perhaps the dust astronomers are seeing isn’t carbon-rich PAHs and graphites.
According to a press release, based on exactly which wavelengths the observed dust is absorbing, lead author Joris Witstok of Sidney Sussex College in Cambridge, England, suspects the dust might instead be a mix of diamond-like or graphite-like grains. These types of grains can be formed in short timeframes by material ejected from supernovae, including those of very massive and short-lived stars. If true, the discovery would fit much more neatly into our current picture of star and dust formation.
Improved models
Before JWST, multiple observations of galaxies had to be combined to observe how their light was affected by dust absorption. Experts were forced to study older galaxies that had had enough time to gather dust and form stars, limiting their ability to pinpoint the sources of cosmic dust. With JWST’s powerful capabilities, scientists can now see light from dwarf galaxies that have existed since the first billion years of cosmic time and observe the origin of their dust in detail.
“We are planning to work further with theorists who model dust production and growth in galaxies,” said study co-author Irene Shivaei of the University of Arizona/Centro de Astrobiología (CAB). “This will shed light on the origin of dust and heavy elements in the early universe.”
This year marks 100 years since the births of two pioneers in the search for life on Mars. Joan Oró and Gilbert V. Levin were part of NASA’s Project Viking, which delivered twin spacecraft to Mars in 1976. Each consisted of an orbiter and a lander probe, carrying a suite of scientific instruments designed to look for life on Mars.
While both Oró and Levin worked directly on instruments for Viking, they had very different interpretations of the mission’s scientific findings. I was fortunate to meet both during the early 2000s. I talked with them extensively about the experiments conducted by the two landers —Viking Lander 1, which touched down at a site called Chryse Planitia on July 20 (exactly 7 years after humans first landed on the Moon) and Viking Lander 2, which set down at Utopia Planitia about 4,000 miles (6,500 kilometers) away on September 3.
One of the most perplexing Viking results was from an instrument called the labeled release (LR) experiment, because it produced seemingly positive results for life at both landing sites. Viking’s other instruments (and scientific consensus) disagreed, but Levin, the LR’s principal investigator, was still calling it a positive result some three decades after the experiment had come to an end. He remained convinced that he’d discovered life on Mars for the rest of his life.
Reading the rocks
Born October 26, 1923, in Lleida, Catalonia, Spain, Joan Oró was a biochemist whose work focused on the origins of life. His research took place largely at the University of Houston. In 1959, Oró demonstrated that adenine — one of a handful of nitrogenous bases that DNA and RNA use to carry genetic information — could form from simpler chemicals in the absence of biology. Six years prior, in a famous experiment at the University of Chicago, graduate student Stanley Miller and chemist Harold Urey had demonstrated abiotic (without biology) synthesis of various biologically important chemicals under conditions thought to have characterized the early Earth. Oró’s achievement continued this path toward understanding how life might have begun.
Nearly a half century later, I was doing research in that same university department, connected with my astrobiology training based at NASA’s Johnson Space Center. When I met Oró in the early 2000s, he was a Professor Emeritus, spending part of the year in Houston and part in Barcelona, work he continued until his death in 2004. During one of his visits in Houston, I interviewed Oró about an instrument he worked on called the gas chromatograph mass spectrometer (GCMS), which examined the regolith at both Viking landing sites to determine its makeup, in particular whether it contained any organic materials — the building blocks of life.
It’s in the air
Born April 23, 1924, Gil Levin developed his instrument for decades before the Viking launch. I met him at a conference of the Mars Society around the turn of the 21st century. At that point, not only was he still publishing papers explaining the rationale behind his belief in the experiment’s results, but he had developed an improved version of the experiment. He even launched the instrument on a Russian mission to Mars, but the spacecraft failed. For the rest of his life, until his death in 2021 at the age of 97, Levin kept trying to get his improved LR onto a Mars mission, but NASA never approved it.
Working as an engineer in the late 1940s and 50s, Levin was recruited to work on detection of bacteria in environmental water samples, using a technique in which small organic compounds — potential food for any bacteria — were supplied to water samples. Metabolism by the bacteria would produce gas, causing visible bubbles. But since the process took so long, bubbles would often appear too late to aid public health applications.
Levin modified the equipment to use carbon-14, a radioactive isotope of carbon, as a marker for any liberated gas. That way, metabolism of the food by microorganisms would be revealed long before any bubbles would be visible. This ultimately led Levin to develop the instrument to send to Mars on Project Viking.
Many organic molecules are chiral, meaning that they can occur in two mirror-image forms (like your right and left hands). While abiotic reactions produce both forms equally, life on Earth requires “left-handed” molecules over their right-handed mirror image. Scientists don’t understand why, but life’s preference for leftie molecules is well established.
So Levin proposed sending the LR instrument with left-handed and right-handed “snacks” for potential microorganisms. Just like with water samples, they would look for carbon-14 as a sign that the snacks had been consumed. If this happened with substrates of one mirror image, but not with the other, it would indicate life, because nonbiological processes don’t discriminate between left- and right-handed.
But due to weight restrictions for the instruments, Levin needed to downsize the LR and have just one mixture of nutrients. And so, instead of chirality, the experiment had to be controlled with heat, available from an oven included with other instruments.
In this version of the experiment, scientists assumed that high temperatures would destroy microbial life, as it does on Earth. So if gas were detected from only the unheated sample, that would indicate biological activity. At both landing sites, that is what actually happened: Gas was liberated from unheated martian regolith samples after they received the nutrient liquid, but not from samples that were heated (sterilized) prior to testing.
The conflict
But Oró’s chemistry instrument, the GCMS, seemed to detect no organic compounds in that same regolith. If there was life, where were the dead bodies? That’s how astronomer and science communicator Carl Sagan explained it on the original Cosmos television series. The apparent lack of organic matter in the martian regolith made most of the science team, including Oró, favor a hypothesis put forth by the principal investigator of a different Viking biology experiment, Vance Oyama. He thought that Levin’s gas release had come from hydrogen peroxide present in the regolith.
It was a simplified hypothesis that doesn’t really have any more evidence than the biological interpretation does, although in the years following, other scientists came up with a complicated model in which different chemicals in the regolith might have caused the positive LR results along with the observed differences between the heated and unheated samples. Over the years, the interpretation of the Viking GCMS finding would come under scrutiny for other reasons, but in my interview of Oró around the year 2000, he said it went “poof.”
I found neither Levin’s nor Oró’s explanation particularly convincing, but during the years that I was talking with Levin, reading his papers, and occasionally presenting work in the same conferences and sessions where he presented, I found his improved LR instrument idea intriguing. He wanted to send it back to Mars with the ability to test the regolith separately with left-handed versus right-handed organic molecules. This is still an excellent idea for distinguishing biological from nonbiological chemical changes.
As we look to Mars and other worlds, I hope that chirality will be at center stage when we are ready, hopefully soon, to send more instruments to Mars, designed to search directly for the activity of life.
After an accidental year-long stay in space, NASA astronaut Frank Rubio and Roscosmos cosmonauts Sergey Prokopyev and Dimitri Petelin successfully landed this morning, Sept. 27, 2023, near the town of Dzhezkazgan, Kazakhstan. The crew initially launched into space on Sept. 21, 2022. After medical exams, the crew will be flown to their hometowns. Cosmonauts Prokopyev and Petelin will be flown to Star City, Russia, while Rubio will board a NASA jet to Houston.
The three crew members spent 371 days in low-Earth orbit aboard the International Space Station (ISS), giving Rubio the record for the longest spaceflight by a U.S. astronaut. The previous mark had been set by NASA’s Mark Vande Hei at 355 continuous days in orbit. The world record for the longest stint in space is held by cosmonaut Valeri Polyakov, who logged 437.7 consecutive days on the Russian space station Mir during 1994 and 1995.
“Frank’s record-breaking time in space is not just a milestone; it’s a major contribution to our understanding of long-duration space missions,” said NASA Administrator Bill Nelson in a press release. “Our astronauts make extraordinary sacrifices away from their homes and loved ones to further discovery. NASA is immensely grateful for Frank’s dedicated service to our nation and the invaluable scientific contributions he made on the International Space Station. He embodies the true pioneer spirit that will pave the way for future exploration to the Moon, Mars, and beyond.”
An extended mission
The milestone comes after Rubio and his fellow crewmates were left stranded on the ISS along with Prokopyev and Petelin after the Russian Soyuz MS-22 spacecraft docked to the station experienced a coolant leak on Dec. 14, 2022. Russian mission control noticed the leak during preparations for a planned spacewalk by Prokopyev and Petelin. According to a NASA blog post, the walk was canceled following the discovery to evaluate the impact on the docked spacecraft.
Roscosmos engineers found that the leak was caused by an impact from a micrometeoroid. They also determined that lacking coolant, the Soyuz MS-22 was unsafe for a normal crew return (though it could be used if there were an emergency on the space station).
On February 23, 2023, the Soyuz MS-23 launched uncrewed as a “rescue” spacecraft to replace MS-22. But to keep the ISS fully crewed, MS-23 was not scheduled to bring the crew back to Earth until the next Soyuz, MS-24 was prepared. As a result, Rubio’s six-month adventure aboard the ISS was extended to a year.
The Soyuz MS-22 module (foreground) suffered a coolant leak after being struck by a micrometeoroid. Credit: NASA/Johnson Space Center
MS-24 launched Sept. 15, bringing a trio of fresh astronauts — finally relieving Rubio, Prokopyev, and Petelin, and clearing the way for them to depart for Earth aboard MS-23.
“Thursday marks a unique milestone for American human spaceflight, and so I would like to take a moment and acknowledge and thank all the people who have helped me to achieve this goal,” Rubio said in a NASA live-streamed news briefing. “So first and foremost, my wife and our four kids, whose resilience and strength have carried me through this entire mission.”
Rubio’s extended mission and first time in space saw him complete 5,936 orbits, NASA said, covering a distance of more than 157 million miles (253 million kilometers), equivalent to about 328 trips to the Moon and back. The agency also noted that the unusual length of Rubio’s stay allowed researchers to observe the effects of long-duration flights — a key issue as NASA prepares for the Artemis missions to the Moon and potential missions to Mars.
When Rubio was asked about what he is looking forward to on Earth, he listed: silence and relief from the noisy hum of the ISS, relaxing in his backyard, and eating a big, green, fresh salad.
What’s next?
As the trio prepared to return to Earth, on Sept. 26, Prokopyev formally handed over his command of the space station to European Space Agency (ESA) astronaut Andreas Mogensen. The departure of Rubio, Prokopyev, and Petelin marks the beginning of Expedition 70 aboard the ISS. The Expedition 70 crew are cosmonauts Nikolai Chub, Konstantin Borisov, and Oleg Kononenko; Japan Aerospace Exploration Agency (JAXA) astronaut Satoshi Furukawa; and NASA astronaut Loral O’Hara; ESA astronaut and Expedition 70 Commander Andreas Mogensen, and NASA astronaut Jasmin Moghbeli. Together, they will continue research and maintenance on the ISS.
In June, astronomers reported a disappointing discovery: The James Webb Space Telescope failed to find a thick atmosphere around the rocky planet TRAPPIST-1 C, an exoplanet in one of the most tantalizing planetary systems in the search for alien life.
The finding follows similar news regarding neighboring planet TRAPPIST-1 B, another planet in the TRAPPIST-1 system. Its dim, red star hosts seven rocky worlds, a few of which are in the habitable zone — at a distance from their star at which liquid water could exist on their surfaces and otherworldly life might thrive.
What it would take to detect that life, if it exists, isn’t a new question. But thanks to the JWST, it’s finally becoming a practical one. In the next few years, the telescope could glimpse the atmospheres of several promising planets orbiting distant stars. Hidden away in the chemistry of those atmospheres may be the first hints of life beyond our solar system. This presents a sticky problem: What qualifies as a true chemical signature of life?
“You’re trying to take very little information about a planet and make a conclusion that is potentially quite profound — changing our view of the whole universe,” says planetary scientist Joshua Krissansen-Totton of the University of Washington.
To detect such a biosignature, scientists must find clever ways to work with the limited information they can glean by observing exoplanets.
When a planet is in front of its star, some of the starlight is absorbed by molecules in the planet’s atmosphere. A telescope trained on the star observes the light that is not absorbed; this creates a spectrum with dips where the light is missing. Above, each dip is the signature of a particular molecule in the spectrum of a hypothetical Earth-like exoplanet. Credit: Adapted from NASA, ESA, CSA, STSCI, JOSEPH OLMSTED (STSCI)
Chemicals in context
Even the most powerful telescopes, including the JWST, almost never “see” exoplanets — by and large, astronomers know these distant worlds only by the flickering of their stars.
Instead of viewing planets directly, astronomers train their telescopes on stars and wait for planets to “transit,” or pass between, their sun and the telescope. As a planet transits, a bit of starlight filters through its atmosphere and dims the star at certain wavelengths, depending on the chemicals in the atmosphere. The resulting dips and peaks in the star’s brightness are like a chemical barcode for the transiting planet.
Perhaps the most intuitive way to look for a biosignature in that barcode is to scour it for a gas that was clearly produced by life. For a time scientists thought that oxygen, which is abundant on Earth because of photosynthesis, served as a stand-alone biosignature. But oxygen can arise from other processes: Sunlight could break apart water in the planet’s atmosphere, for example.
And that problem isn’t unique to oxygen — most of the gases that living things produce can also arise without life. So instead of treating single gases as biosignatures in their own right, scientists today tend to consider them in context.
Methane, for instance, can be produced both with and without life. It wouldn’t be a convincing biosignature on its own. But finding methane and oxygen together “would be hugely exciting,” says planetary scientist Robin Wordsworth of Harvard University; it’s very difficult to produce that combination without life. Likewise, work by Krissansen-Totton and colleagues recently showed that finding methane along with the right amounts of other gases, such as carbon dioxide, would be hard to explain without life.
Watching how an exoplanet atmosphere changes over time might also provide valuable context that could strengthen otherwise weak biosignatures. Seasonal variations in the concentration of ozone, for example, could be a fingerprint of life, scientists reported in 2018.
Surprises, not assumptions
Of course, “if you’re looking for individual gases like oxygen or methane, then built into that are assumptions about what type of life is elsewhere,” says Krissansen-Totton. So some scientists are developing agnostic biosignatures that don’t assume alien biochemistry will be anything like Earth’s biochemistry.
One possible agnostic biosignature is an exoplanet atmosphere’s degree of chemical “surprisingness” — what scientists call chemical disequilibrium.
An atmosphere close to equilibrium would be chemically uninteresting, a bit like a closed flask of gas in a laboratory. Of course, no planet is as boring as a lab flask. Chemical reactions in a planet’s atmosphere can be powered by their stars and geological processes like volcanic activity can increase disequilibrium, and thus increase the chemical surprisingness of the atmosphere.
Telescopes like the JWST that are trained on distant planets may observe the signatures of particular elements or molecules in the planet’s atmosphere, which are revealed in the peaks and valleys of transmitted light. But the signature of a molecule doesn’t explain its origin: A similar signature might arise from very different planetary processes, whether active volcanoes, frozen oceans or biological activity.
Life can also push planets away from equilibrium. And assuming that alien life produces gases of some kind, they could push a planet’s atmosphere much further from equilibrium than it would be otherwise. Yet disequilibrium alone “is not an unambiguous indicator,” says Krissansen-Totton.
In 2016, he and his colleagues calculated the thermal disequilibrium of the atmosphere of every planet in the solar system and Saturn’s moon Titan. By this measure, the Earth’s atmosphere stood out as extreme — but only if the oceans were built into the calculations. Ignoring its interactions with the ocean, the Earth’s atmosphere is actually closer to equilibrium than the atmosphere of Mars.
Still, even if it might not point to biology, finding an exoplanet atmosphere far from equilibrium would tell astronomers that something interesting is happening, Krissansen-Totton says, something that’s “modifying the atmosphere in a dramatic way that we need to understand.”
David Kinney, a philosopher of science at Yale University, recently worked with biophysicist Chris Kempes of the Santa Fe Institute to develop a new way of detecting possible agnostic biosignatures. It’s a deceptively simple idea: To find life, look for the weirdest planets.
If no assumptions are made about what alien life is like, practically any gas could be a biosignature in the right context. In 2016, MIT astrophysicist Sara Seager and colleagues proposed a list of about 14,000 molecules for consideration as possible biosignatures. Kinney and Kempes developed their assessment method by using that list of compounds, along with methods inspired by machine learning algorithms designed to recognize the odd-image-out in a set. This led to a way to precisely define and score the “weirdness” of a hypothetical exoplanet’s atmosphere compared to a set of other hypothetical atmospheres.
Kinney and Kempes argue that the weirdest atmospheres in a set are the most likely to host life. This rests on a few basic assumptions: Life in the universe is rare, it leaves traces in planetary atmospheres, and it’s hard to mimic those traces without life. Of course, those assumptions might turn out to be false, Kinney says. But “if we want to make no assumptions at all,” he adds, “then I think it’s very hard to make any kind of scientific progress, let alone in the area with such severe uncertainty as this one.”
Scientists first confirmed the existence of exoplanets in 1992 and the discoveries have been coming fast and furious ever since. Credit: NASA/JPL-CALTECH
First, understand non-life
To reduce that uncertainty, scientists will need to be able to confidently rule out non-life explanations for any potential biosignature. That requires a thorough understanding of alien geology and atmospheric chemistry. So instead of focusing on whether a planet is habitable, some scientists argue that studying obviously lifeless planets will bolster the search for alien life.
“There are so many really basic things that I think we need to learn about the planets first before we can even begin to ask the question of habitability,” says Laura Kreidberg of the Max Planck Institute for Astronomy in Germany, coauthor with Wordsworth of an overview of rocky exoplanet astronomy in the 2022 Annual Review of Astronomy and Astrophysics.
One enormous question is whether the potentially rocky planets that JWST can observe will have atmospheres at all. The only stars whose habitable-zone planets are within the telescope’s reach are red dwarfs, like TRAPPIST-1. These stars have a nasty habit of spewing harsh radiation that many scientists think would inevitably strip away the atmospheres of any habitable planets, which might explain the scant or nonexistent atmospheres of TRAPPIST-1 B and TRAPPIST-1 C.
Red dwarf stars also happen to be the most common in the Milky Way — so if their rocky planets can’t hold on to atmospheres, it would substantially winnow down the number of potentially habitable worlds.
If we can observe enough rocky exoplanets, “we’re going to be in a much, much stronger place to understand what a biosignature means,” says Wordsworth. “One really powerful thing that exoplanets give us is statistics.”
The word “biosignature” may evoke a smoking gun. But, says Krissansen-Totton, “exoplanet life discovery is going to be a gradual accumulation of evidence.”
As that evidence continues to roll in, scientists can begin to test their hypotheses about rocky planets in a rigorous way, and perhaps reevaluate them.
“Astronomy is, at its heart, such a discovery science,” says Kreidberg. “For all of our best-laid plans and frameworks and systems, as soon as we start getting data and observing things, everything turns upside down.”
Elise Cutts is one of those ex-scientists who realized that writing about research is more fun than doing it. She’s based in Graz, Austria; find her @elisecutts.
This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter.
A recent discovery has unveiled the death scene of a large star, three times the mass of the Sun, being torn apart by the menacing gravitational forces of a supermassive black hole. An event like this is called a tidal disruption event (TDE). But this particular case, called ASASSN–14li, is unique for a multitude of reasons.
Two of the most important reasons: This star is one of the largest stars ever recorded undergoing a TDE and one of the closest discovered in the past decade, located just 290 million light-years away. Due to the relatively close proximity and unusual size of the star, astronomers were able to obtain key details to some unanswered mysteries behind the process of this event. The team published their results Aug. 20 in The Astrophysical Journal Letters.
Detecting TDEs
Although it’s commonly said that nothing can escape a black hole’s grasp, it’s entirely possible for a black hole interaction to occur without a luminous object disappearing into the black hole.
As an object nears a black hole, it experiences a tidal force that can stretch it apart, causing it to shed material in a TDE. But astronomers are not certain how this process begins. Hypothetically, once inside the tidal disruption radius of a black hole, the star gets turned inside-out and its material begins traveling at incredibly high speeds, creating a bright stream toward the black hole. Alternatively, the material can also become unbound. Even as this happens, the star continues its orbit and undergoes a TDE each trip around the black hole, which eventually forms a small accretion-like disk.
Forensic telescopes
Now clues — in the form of X-rays from ASASSN–14li — have confirmed this idea. X-ray data captured using NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton space telescopes have allowed scientists to retrace the scene of the crime for this massive star.
“These X-ray telescopes can be used as forensic tools in space,” said co-author Brenna Mockler of Carnegie Observatories and the University of California, Los Angeles, in a press release.
X-ray observations allow the analysis of hot spots, in which particles reach high temperatures as they are energized either by huge explosions or the intense gravitational field. Additionally, using these telescopes to observe at different wavelengths produces an X-ray spectrum for the scene, showing the chemical composition of the material that’s glowing.
The Chandra spectrum reveals that “the relative amount of nitrogen to carbon that we found points to material from the interior of a doomed star,” said Mockler. Fortunately for us, th material is being pushed toward Earth and away from the supermassive black hole, as confirmed by a blueshift in the color of the light. (A more familiar redshift occurs when material is moving away from Earth.) The spectrum accentuates an abundance of nitrogen and the lack of carbon, which validates the star’s mass of three times the Sun’s mass. Now, any models astronomers use can be fine-tuned to more accurately tell the ongoing murder story for this stellar victim. “ASASSN–14li is exciting because one of the hardest things with tidal disruptions is being able to measure the mass of the unlucky star,” said co-author Enrico Ramirez-Ruiz of the University of California, Santa Cruz.
Reconstructing the crime scene
By obtaining data from ASASSN–14li and other similar TDEs, improved models can be produced to estimate the amount of nitrogen and carbon that exists around the black hole. Particularly, using NASA’s Neil Gehrels Swift Observatory, scientists have already been able to create an automated search of X-ray emitting TDEs to keep a vigilant watch on these phenomena.
And with a combination of findings, astronomers will have the chance to identify the possible presence of star clusters surviving in the harsh environment around supermassive black holes in distant galaxies.
Cowboy Nicolas Silva enjoys his view of the total solar eclipse on July 2, 2019, from atop a mountain ridge near Cabalgatas Altos de Cochiguaz, a ranch in Chile’s Elqui Valley.
Rick Armstrong
1. Take eclipse day off — now!
Spring may still seem like a long way off, but April 8, 2024, may turn out to be a very popular vacation-day request. If you’re considering checking out an eclipse, be sure to get that vacation request in now and mark it on your calendar.
2. Make a weekend out of it
Eclipse day in 2024 is a Monday. Lots of related activities in cities that will experience totality during the 2024 total solar eclipse will occur on Saturday and Sunday. Find out what they are, where they’re being held, and which you want to attend, and make a mini-vacation out of the eclipse. Events like cruises to exotic locations will allow you to experience the full social impact of the eclipse.
3. Attend an event
You’ll enjoy the eclipse more if you hook up with like-minded people. If you don’t see any special goings-on a few months before April 8, call your local astronomy club, planetarium, or science center. Anyone you talk to is sure to know about eclipse activities.
4. Get involved
If your interests include celestial events and public service, consider volunteering with a group putting on an eclipse event. You’ll learn a lot and make some new friends in the process. And don’t forget to brush up on your 2024 total solar eclipse trivia!
5. Watch the weather
Average April cloud cover, 2000-2020
The track of the 2024 total solar eclipse is overlaid on this map of the average cloud cover during April (2000-2020) at approximately 1:30 pm local time, as measured by the Aqua spacecraft.
Jay Anderson/Fred Espenak
Meteorologists study a chaotic system. Nobody now can tell you with certainty the weather a specific location will experience on eclipse day. And don’t get too tied up in the predictions of cloud cover you’ll see for that date. Many don’t distinguish between “few” (one-eighth to two-eighths of the sky covered), “scattered” (three-eighths to four-eighths), or “broken” (five-eighths to seven-eighths) clouds and overcast. Also, many of the “predictive” websites use satellite data, which detects much more cloudiness than human observers. In both cases, you need to dig deeper.
6. Stay flexible on eclipse day
Unless you are certain April 8 will be clear, don’t do anything that would be hard to undo in a short time. For example, let’s say you’re taking a motor home to a certain city. You connect it to power, hook up the sewage hose, extend the awnings, set up chairs, start the grill, and more. But if it’s cloudy six hours, three hours, or even one hour before the eclipse starts, you’re going to want to move to a different location. Think of the time you would have saved if you had waited to set up. Also, the earlier you make your decision to move, the better. Just imagine what the traffic might be like on eclipse day.
7. Don’t plan anything funky
Totality during the 2024 total solar eclipse will be the shortest four and a half minutes of your life. All your attention should be on the Sun. Anything else is a waste. And be considerate of those around you; please, no music.
8. Pee before things get going
Yes, this statement could be phrased more politely, but you needed to read it. And follow it. This tip, above and beyond any other on this list, could be the most important one for you. Don’t wait until 10 minutes before totality to start searching for a bathroom. Too much is happening then. Make a preemptive strike 45 minutes prior.
9. Notice it getting cooler?
A basic smartphone or a point-and-shoot camera that takes video will let you record the temperature drop. Here’s a suggestion: Point your camera at a digital thermometer and a watch, both of which you previously attached to a white piece of cardboard or foam board. Start recording video 15 or so minutes before totality and keep shooting until 15 minutes after. The results may surprise you.
10. Watch for the Moon’s shadow
If your viewing location is at a high elevation, or even at the top of a good-sized hill, you may see the Moon’s shadow approaching. This sighting isn’t easy because as the shadow crosses Indianapolis, for example, it is moving at 1,992 mph (3,206 km/h), or more than 2½ times the speed of sound. Another way to spot the shadow is as it covers thin cirrus clouds, if any are above your site. Again, you’ll be surprised how fast the shadow moves.
Upcoming eclipse paths, 2009-2028
This chart shows the paths of totality for 15 solar eclipses occurring between 2009 and 2028.
Astronomy: Roen Kelly after Fred Espenak, NASA/Goddard Space Flight Center
11. View the 360° sunset
During totality, take just a few seconds to tear your eyes away from the sky and scan the horizon. You’ll see sunset colors all around you because, in effect, those locations are where sunset (or sunrise) are happening.
12. Get a filter in advance
Cardboard “eclipse” glasses with lenses of optical Mylar cost about $2. Such a device — it’s not a toy — will let you safely look directly at the Sun. It filters out most of the light, all of the dangerous infrared (heat) and ultraviolet radiation, which tans our skin. Buy one well in advance, and you can look at the Sun anytime. Sometimes you can see a sunspot or two. That’s cool because to be visible to our eyes, such a spot has to be larger than Earth. Another safe solar filter is a #14 welder’s glass, which also will cost you $2. Wanna look cool at the eclipse? Buy goggles that will hold the welder’s glass. I’ve even seen people wearing whole helmets. Either those or goggles serves one purpose — you won’t need to hold the filter, so you can’t drop it.
13. No filter? You can still watch
Except during totality, we never look at the Sun. But what if you’ve forgotten a filter? You can still watch by making a pinhole camera. It can be as simple as two pieces of paper with a tiny hole in one of them. (Try to make the hole as round as you can, perhaps with a pin or a sharp pencil.) Line up the two pieces with the Sun so the one with the hole is closest to it. The pinhole will produce a tiny image, which you’ll want to have land on the other piece of paper. Moving the two pieces farther apart will enlarge the Sun’s image but will also lessen its brightness. Work out a good compromise.
14. Bring a chair
In all likelihood, you’ll be at your viewing site several hours before the eclipse starts. You don’t really want to stand that whole time, do you?
15. Don’t forget the sunscreen
Even though the eclipse happens in early April, you’ll be standing around or sitting outside for hours. You may want to bring an umbrella for some welcome shade, especially if you’re viewing the event from the Southwest. And if you see someone who has forgotten sunscreen, please be a peach and share.
16. Take lots of pictures
Before and after totality, be sure to record your viewing site and the people who you shared this great event with. Social media has become the preferred way to do this.
17. The time will zoom by
In the August 1980 issue of Astronomy magazine, author Norm Sperling contributed a “Forum” titled “Sperling’s 8-second Law” in which he tries to convey how quickly totality seems to pass. I’ll just quote the beginning here.
“Everyone who sees a total solar eclipse remembers it forever. It overwhelms the senses, and the soul as well — the curdling doom of the onrushing umbra, the otherworldly pink prominences, and the ethereal pearly corona. And incredibly soon, totality terminates.
“Then it hits you: ‘It was supposed to last a few minutes — but that couldn’t have been true. It only seemed to last eight seconds!’”
18. Bring snacks and drinks
You’re probably going to get hungry waiting for the eclipse to start. Unless you set up next to a convenience store, consider bringing something to eat and drink.
19. Not many people you meet will have seen totality
If you’re planning an event or even a family gathering related to the eclipse, consider this: Statistically, only a few percent of the people you encounter will have experienced darkness at noon. You will be the expert. A telescope equipped with an approved solar filter will help Sun-watchers get the most from the eclipse.
20. Invite someone with a solar telescope
In the event you’re thinking of hosting a private get-together, make sure someone in attendance brings a telescope with a solar filter. While it’s true that you don’t need a scope to view the eclipse, having one there will generate quite a bit of buzz. And you (or the telescope’s owner) can point out and describe sunspots, irregularities along the Moon’s edge, and more.
The red spots at the top of the corona of the Sun during the total solar eclipse are called Bailey’s beads. This image was taken during the Great American Eclipse of 2017.
NASA/Carla Thomas
21. Experience totality alone
The 2024 total solar eclipse plus the events leading up to it will combine to be a fabulous social affair. Totality itself, however, is a time that you might want to mentally shed your surroundings and focus solely on the sublime celestial dance above you. You’ll have plenty of time for conversations afterward. A get-together with family and friends after the eclipse will help you unwind a bit and hear what others experienced.
22. Schedule an after-eclipse party or meal
Once the eclipse winds down, you’ll be on an emotional high for hours, and so will everyone else. There’s no better time to get together with family and friends and just chat. Or, take a secondary position and just listen to others talking about what they’ve just experienced. Fun!
23. Record your memories
Sometime shortly after the eclipse, when the event is still fresh in your mind, take some time to write, voice-record, or make a video of your memories, thoughts, and impressions. A decade from now, such a chronicle will help you relive this fantastic event. Have friends join in, too. Stick a video camera in their faces and capture 30 seconds from each of them. You’ll smile each time you watch it.
24. Don’t photograph the eclipse
This tip — specifically directed at first-time eclipse viewers — may sound strange because it’s coming to you from the former photo editor of the best-selling astronomy magazine on Earth. But I’ve preached this point to thousands of people who I’ve led to far-flung corners of our planet to stand under the Moon’s shadow. True, few of them have thanked me afterward. But I can tell you of upwards of a hundred people who have told me with trembling voices, “I wish I’d followed your advice. I spent so much time trying to center the image and get the right exposures that I hardly looked at the eclipse at all.” How sad is that? And here’s another point: No picture will capture what your eyes will reveal. Trust me, I’ve seen them all. Only the top 1 percent of the top 1 percent of photographers have ever come close. And — no offense meant — but you, with your point-and-shoot pocket camera, off-the-shelf DSLR, or cutting-edge smartphone, are not one of them.
25. Do not photograph the eclipse!!!
This appears twice for emphasis. Why, oh why, would you even consider looking down and fiddling with a camera when you could be looking up at all that heavenly glory? The 2024 total solar eclipse will — at maximum — last 268 seconds. That’s it, friends. If your camera isn’t doing what you think it should, you’re going to lose valuable time adjusting it. There will be plenty of pix from imagers who have viewed a dozen of these events. So just watch. Watch your first eclipse with your mouth agape, where your only distraction is occasionally wiping tears of joy from your eyes. You will not be disappointed.
Many people, even astronomy enthusiasts, routinely wonder about the frequent reports of UFOs, or UAPs (unidentified anomalous phenomena), frequently spotted in the sky and sending people into fits over alien visitation. But the people who are sincerely worried about that have never taken the first week of an academic course on what astronomers call the cosmic distance scale.
In the words of the popular writer Douglas Adams, author of A Hitchhiker’s Guide to the Galaxy, “Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”
And Adams is exactly right. Let’s begin by considering local space. Assume that the distance between Earth and the Sun, known as 1 astronomical unit, is 1 centimeter instead of its actual 93 million miles. In all of human history, mind you, we have physically traveled an imperceptibly small fraction, then, of that 1 centimeter.
Comparing cosmic distance scale
You can think of a scale model solar system in your room, your neighborhood, and your town. On that scale, Jupiter would be 5 cm from the Sun. Keep moving off, say, to the right, and imagining the relative distances. Saturn would be 10 cm from the Sun, Uranus 19 cm from the Sun, and Neptune 30 cm from the Sun. Little old Pluto would typically be about 40 cm from the Sun.
On this scale, however, the physical diameter of the solar system is far larger than that. The outer edge of the Oort Cloud, the enormous shell of perhaps a trillion comets, would lie 10 football fields away. And we have, thus far, traveled a tiny, almost invisible fraction of that original 1 cm.
And that’s just our solar system. The nearest star, Proxima Centauri, is four times farther away than the outer shell of the Oort Cloud. The enormous gap between even the nearest stars would be staggeringly large. The actual distance to Proxima Cen is 4.2 light-years, meaning that light — the fastest thing there is — takes 4.2 years to travel from that star to our eyes.
We can take quantum leaps upward in universal scale, too. The Milky Way Galaxy is one of at least 100 billion galaxies in the cosmos. The diameter of the Milky Way’s bright disk, which we are in, is at least 100,000 light-years. (We are a little more than 26,000 light-years out from the galaxy’s center.) The most distant photons from our own galaxy have been traveling to us for one-third of the length of human history.
And a little like nesting dolls, we can follow cosmic structures out to larger and larger scales. Our Local Group of galaxies, as Edwin Hubble termed it back in the 1930s, contains at least 55 galaxies in a sphere spanning about 10 million light-years. Local Group members include our nearby friends the Andromeda Galaxy and the Triangulum Galaxy.
Countless small groups of galaxies are even farther away, and if we travel some 55 million light-years, we get to the center of the largest cluster of galaxies in our cosmic space, the Virgo Cluster. This group includes some 1,300 galaxies of all types. But larger and more massive groups of galaxies lie far more distantly from us. Nearly countless numbers of them.
When we get up to the largest cosmic structures known, we can talk about superclusters and walls of galaxy clusters. Examples include Laniakea, which we belong to, a structure that stretches some 500 million light-years across. And there are dozens of examples of other large structures.
The universe could, indeed, be infinite
How large is the universe? Put simply, we don’t know. The best current estimate is that the universe’s diameter is at least 93 billion light-years. And if cosmic inflation is correct (a long story, but a likelihood), then the visible universe that we see may not be the whole thing. As much as it sounds like science fiction, the universe could actually be infinite in size. And of course whatever its size, we know that the universe is expanding over time, and that this expansion is accelerating over time as well.
Thankfully, we can see the distant universe as it was long ago because photons are massless, and they travel at 186,000 miles per second, the fastest speed there is. The folks who are perplexed or anguished by reports of UFOs not only don’t appreciate the unbelievably vast cosmic distance scale. They also don’t understand that only massless objects, photons, can travel at such high velocities. Things with mass require a tremendous amount of energy to convert into high-speed motion. Don’t believe me? Try eating a tuna sandwich and running around the circumference of Earth a few times before taking up a rest. You’ll get it then.
So the universe may be teeming with life (that’s a topic for another time), but it is so distant that we will not encounter it staring us in the face, accompanying us to lunch in Central Park. That’s the stark reality that trained astronomers know.
When you pick up a meteorite, you are holding an ancient piece of the solar system right in your hands. Most meteorites come from asteroids, which are debris left over from the violent, chaotic formation of the solar system. There are three categories of meteorites — iron, stone, and stony-iron; they originate from an asteroid’s core, mantle, or the boundary between the core and mantle.
Some meteorites even come from other worlds — the Moon or Mars; these rocks were blown off by an impact and eventually made their way across the solar system to fall to Earth.
You can start your own collection of meteorites by checking online dealers like My Science Shop. You can also go to the Tucson Gem Show, which takes place every year in February.
Following the only deaths to have ever occurred in space, the USSR started a policy requiring all cosmonauts to wear pressurized spacesuits during reentry. Credit: Peakpx.com.
For many wannabe astronauts, the idea of venturing into the great unknown would be a dream come true. But over the past 50 years, there’s been a slew of spaceflight-related tragedies that are more akin to an astronaut’s worst nightmare.
In the last half-century, about 30 astronauts and cosmonauts have died while training for or attempting dangerous space missions. But the vast majority of these deaths occurred either on the ground or in Earth’s atmosphere — below the accepted boundary of space called the Kármán line, which begins at an altitude of about 62 miles (100 kilometers).
However, of the roughly 550 people who have so far ventured into space, only three have actually died there.
The fatal frontier
Early in the space race, both NASA and the USSR experienced a surge in deadly jet crashes that killed a number of pilots testing advanced rocket-propelled planes. Then, of course, there was the Apollo 1 fire in January 1967, which killed astronauts Gus Grissom, Ed White, and Roger Chaffee in a horrific manner. During a launch simulation, a stray spark within the cabin of the grounded spacecraft, which was filled with pure oxygen, ignited. This led to an uncontrollable fire that quickly overwhelmed the doomed crew, leading to their tragic deaths as they struggled in vain to open the pressurized hatch door.
Astronaut Gus Grissom’s flight suit following the Apollo 1 fire in 1967, which killed Grissom, Ed White, and Roger Chaffee. National Archives
“We had done exactly the same test the night before but without the hatch closed, so we weren’t on 100 percent oxygen,” Walter Cunningham, Lunar Module Pilot of Apollo 7, told Astronomy. “So, when the [Apollo 1] crew died, it was a couple of weeks later before they started picking up the pieces, and at which point we were assigned the prime crew of the first manned Apollo mission.” A little less than two years later, in October 1968, Cunningham, Wally Schirra, and Donn Eisele became the first Apollo crew to successfully venture into space.
Over the next three years, Apollo astronauts completed seven more missions — including the first Moon landing during Apollo 11 and the ill-fated Apollo 13 mission. Then, on June 30, 1971, humankind witnessed the first (and, so far, only) deaths to occur in space.
The Soyuz 11 disaster
The first space station to park itself above Earth’s atmosphere was the USSR’s Salyut 1, which launched (unmanned) on April 19, 1971. Just a few days later, a crew of three Soviets blasted off aboard Soyuz 10 with the goal of entering the space station and staying in orbit for a full month. Though the Soyuz 10 crew docked safely with the Salyut 1, issues with the entry hatch prevented them from entering the space station. During their premature return trip back to Earth, toxic chemicals leaked into the air supply of Soyuz 10, causing one cosmonaut to pass out. However, all three members of the crew ultimately made it home safe with no long-lasting effects.
Just a few months later, on June 6, the Soyuz 11 mission took another crack at accessing the space station. Unlike the previous crew, the three Soyuz 11 cosmonauts — Georgi Dobrovolski, Vladislav Volkov, and Viktor Patsayev — successfully entered Salyut 1. Once aboard, they spent the next three weeks not only setting a new record for the longest time spent in space, but also carrying out loads of experiments focused on how the human body deals with extended periods of weightlessness.
Cosmonauts Georgi Dobrovolski (left), Vladislav Volkov (middle), and Viktor Patsayev (right), the only three people to die in space, are featured on three USSR stamps. USSR Post
On June 29, the cosmonauts loaded back into the Soyuz 11 spacecraft and began their descent to Earth. And that’s when tragedy struck.
To those on the ground, everything about Soyuz 11’s reentry seemed to go off without a hitch. The spacecraft appeared to make it through the atmosphere just fine, ultimately landing in Kazakhstan as planned. It wasn’t until recovery crews opened the hatch that they discovered all three crew members inside were dead.
After discovering the unresponsive Soyuz 11 crew, recovery teams futilely attempted CPR, seen here in this screenshot of declassified footage that appeared in the the Russian TV documentary “Death of the Soyuz.” youtu.be/DdhwbvKMe3I
“Outwardly, there was no damage whatsoever,” recalled Kerim Kerimov, chair of the State Commission, in Ben Evans’ book Foothold in the Heavens. “[The recovery crew] knocked on the side, but there was no response from within. On opening the hatch, they found all three men in their couches, motionless, with dark-blue patches on their faces and trails of blood from their noses and ears. They removed them from the descent module. Dobrovolski was still warm. The doctors gave artificial respiration. Based on their reports, the cause of death was suffocation.”
The fatal accident was determined to be the result of a faulty valve seal on the spacecraft’s descent vehicle that burst open during its separation from the service module. At an altitude of 104 miles (168 km), the deadly combination of a leaking valve and the vacuum of space rapidly sucked all the air out of the crew cabin, depressurizing it. And because the valve was hidden below the cosmonauts’ seats, it would have been nearly impossible for them to fix the problem in time.
During an early NASA vacuum test, Jim Leblanc’s pressurized suit began to lose air, leading to decompression. Within about 30 seconds, he passed out, but his coworkers fortunately were able to get to him in time to save his life.
As a direct result of the decompression deaths of the Soyuz 11 crew, the USSR quickly made the shift to requiring all cosmonauts to wear pressurized space suits during reentry — a practice that’s still in place today.
Scientists could soon use common lab technology along with sophisticated algorithms to answer one of the biggest questions in all of astronomy — are we alone in the universe?
In new research published today in Proceedings of the National Academy of Sciences (PNAS), a team of scientists announced a novel technique that can take a sample of a material, feed it through a machine-learning algorithm, and find out if the material did — or didn’t — come from a living organism with 90 percent accuracy.
Cracking the code
Current technology is sophisticated enough that, if you placed it in a future Mars rover, it could take a given sample of material and find out if it contains traces of life, even if martian life is different than our own. The technology, according to study co-author Robert Hazen of the Carnegie Institution for Science, could even fly through the plumes of Europa and sort out the chemistry there — a pretty quick and efficient way to figure out the details of life in our solar system.
The underlying tech is simple enough that it was equipped on NASA’s Mars Viking landers 46 years ago for the famous labeled release experiments that left a big question mark about life on the Red Planet. Called pyrolysis–gas chromatography–mass spectrometry (pyrolysis-GC-MS), it uses heat (hence pyrolysis) to burn a sample of a material. Then a spectrometer breaks down the chemical residue from that material (smoke, for lack of a better term) to determine what chemicals were present. According to Hazen, the tech is found in “just about every organic chemical lab, forensics lab, industry, and more.”
So why didn’t Viking put the question of life on Mars to bed right around the time The Clash was playing its first gigs? Partially, it’s because of the resolution limits of the data. But also it relies on the other half of the current experiment: artificial intelligence. Study lead author Henderson Cleaves likens what the algorithms do to a kind of cryptography, the cracking of codes.
“It’s kind of related to the old days of cryptography where people did simple substitution codes,” Cleaves, a professor at the Tokyo Institute of Technology’s Earth-Life Science Institute, says. “So you’d swap T for E and Z for S and do one-to-one. You could tell what language message was written in just from the frequency of the symbols.”
The team assembled a bunch of materials, some generated by living things, others non-living. “Collecting the samples was really fun,” Hazen says. “Bugs and leaves collected during walks in the woods, contacting old friends for their samples, geology field trips, and even a trip to the beach!”
Finding life elsewhere
The new technology could answer questions about worlds with familiar chemistries, like Mars, Europa, and Enceladus, where water plays a huge role. Even if life arose under different conditions than life on Earth, it will still play by some of the same underlying rules.
But solar system worlds exist that could hold more exotic life. For instance, on Titan, water is frozen as hard as bedrock on the surface, but it is the only body in the solar system to have hydrocarbon rivers and lakes of ethane and methane. A 2015 paper suggested that life on the saturnian moon could use something other than lipids as its cell walls, namely vinyl cyanide, which is present on that world.
Cleaves says the new tech could possibly find life even this exotic on Titan, with its alternative chemistry. A sample would be burned, the spectrometer would analyze it, and from there the algorithm would sift through it. The algorithm would sort it into two categories: chemicals we know to occur in nature, and chemicals that are more anomalous. From the anomalous measurements, you could still find biological markers.
“So, if a [life-form] decided that to adapt to its environment, it needs to be this way and the way that it needs to be is outside of the measured ranges, we would pick that up,” Cleaves says.
But then there’s the next question: What about life beyond our solar system? Recently, the James Webb Space Telescope may have detected traces of a compound called dimethyl sulfide on the exoplanet K2–18b, located 124 light-years from Earth. That planet isn’t much like anything we have in our solar system. Its mass is between that of Earth and Neptune, and it probably hosts an oceanic surface under high gravity. Methane and carbon dioxide suggest the existence of an ocean, but, at least on Earth, dimethyl sulfide is produced primarily by phytoplankton. Because a “Hycean” (hydrogen atmosphere + water ocean, so hydrogen+ocean) world is so different than anything in our solar system, maybe some other process is at work.
For now, it’s a little out of reach, Cleaves says. The algorithm could sort through high-resolution atmospheric spectra for the fingerprints of life. It can be applied to “any type of data,” Cleaves says, including atmospheric spectra. But, he suggests, “I don’t think the spectra we’re able to gather from planets around other stars has enough features or resolution to really use this technique effectively.” As Cleaves points out, we have plenty of intriguing places closer to home to look at, places we could get to in a few months or a few years’ time.
Earthbound applications also exist. The paper uses the example of a contentious mineral deposit found in the Pilbara Craton region of Australia. A debate has raged for a while about samples from this area: Some scientists contend they’re early evidence of life on Earth, at nearly 3.5 billion years old, but others maintain they were produced by a natural, but abiotic, process.
Already, Cleaves says, scientists from around the world are sending in such samples. The team also wants to look at martian meteorites that fell to Earth for traces of life. Medical applications also exist using the ability of the algorithm to sort chemicals to look for cancers or markers of autoimmune diseases that rise from foreign cells making their way into someone via a process called microchimerism.
“There’s just so many applications for this,” Cleaves says. “That’s pretty exciting.”
On Sept. 24, 2023, part of the asteroid belt hit Earth — safely under parachutes and inside a capsule. The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer — better known as OSIRIS-REx — has now successfully dropped off its collected pieces of the near-Earth asteroid Bennu.
The spacecraft’s six-year main mission culminated with the morning re-entry of the sample return capsule holding some eight ounces (227 grams) of primitive asteroid in its clutches. It landed at the Air Force’s Utah Test and Training Range, which lies within the U.S. Army’s Dugway Proving Grounds in Utah’s West Desert.
At 4:42 A.M. local time, when the craft was still some 67,000 miles (107,825 kilometers) from Earth officials considering both the safety of recovery crews and the survivability of the capsule had to make a call.
It was a go. That’s when the sample capsule released from the main spacecraft.
Safe landing
The desert — at turns rolling, flat, or rugged — is vast, home to wild horses, golden eagles, greasewood, and fourwing saltbush. “It’s a beautiful place to land a capsule,” said Rich Burns, the mission’s project manager at NASA’s Goddard Space Flight Center in Baltimore, Maryland, in a press release. He compared getting the capsule on the landing ellipse to throwing a dart and hitting a bull’s-eye from across a basketball court.
The recovery action began just after the Sun came up on a chilly first full day of fall. Four helicopters filled the air with choppy roar and the smell of aviation fuel as they took off from Dugway’s airfield, carrying the team that would prepare the capsule for transport.
According to Sandy Freund, with Lockheed Martin mission operations, four hours passed between the release and re-entry at 27,000 mph (43,450 km/h), with the capsule pulling 30 Gs. But under the main chutes, the capsule touched down at a gentle 11 mph (18 km/h) at 8:52 A.M. MDT, just a few feet from a gravel road.
The sample was transported by helicopter to the facility with a clean room. Credit: NASA/Keegan Barber
The recovery team first visually inspected the capsule from a distance, taking external temperatures and testing for gases in the air and in the craft to determine whether it was safe for approach (an unexploded bolt or ruptured battery would not have been welcome). They then wrapped the capsule and nestled it into a cargo container. The assembly was put into a cargo net for a helicopter to ferry back to the air base, the capsule dangling on a 100-foot-long (30 meters) line.
What ensued was a technical ballet. The helicopter landed outside a hangar where, in an ordinary parking lot, recovery crew rolled the capsule to the hangar on a specially built cart. Throughout the process, personnel consulted each other, checked the capsule’s wrapping, and then, finally, politely knocked twice to gain entry. Inside, the craft was unwrapped so staff could to brush material off the burnt shell and clean the rolling cart’s wheels so no desert grit made its way into the temporary clean room beyond.
Finally, the cart was rolled up a short metal ramp to the clean room’s sealed doors. The capsule was carefully lifted into a second cart made of anodized aluminum, the color of gold. This cart had been used for the Stardust cometary sample return mission nearly 20 years ago, which landed at the same site. Lockheed took it out of storage because that capsule had been the same size as OSIRIS-REx.
Only then did some of Bennu enter the clean room.
Mission success
The clean room, a metal and polycarbonate-window shed set on a concrete floor, had interior pressure higher than the outside to prevent external contamination. NASA and mission logos flanked the front metal doors. Wearing three layers, “fully bunnyed” personnel took off the capsule’s backshell and other equipment. (The sample retrieval unit is inside a canister, which itself is inside the sample return capsule.) They attached a nitrogen purge that will continue to release nitrogen — an inert gas — through the sample canister being stowed in Houston. Apart from safely having the capsule in hand, attaching the purge was the day’s main goal. It will further safeguard against terrestrial contamination, said Nicole Lunning, the team’s curation lead.
Clean room staff process the OSIRIS-REx sample. Credit: NASA/Keegan Barber
Today, those precious bits of Bennu are scheduled to fly on a cargo plane to Ellington Air Force Base in Houston. From there, it’ll be driven to the Johnson Space Center’s Astromaterials Acquisition and Curation Office. That’s where processing of the sample will begin, culminating in its eventual distribution to researchers around the world at 60 different labs.
More immediately, as soon as Sept. 26, principal investigator Dante Lauretta tells Astronomy the team will wipe the canister walls for a “quick-look analysis.” They’ll be looking for clays, carbonates, and iron oxides to see whether the remote sensing instruments were on point when characterizing Bennu’s composition from orbit.
Lauretta was also part of the team that sampled the Utah desert immediately around the landing site to characterize those materials — dirt, air, water, etc. — in case any happened to infiltrate the seal (an event he called “unlikely”).
Picking up pieces
OSIRIS-REx launched Sept. 8, 2016, as the first U.S. asteroid sampling mission. It carried a suite of instruments including the touch-and-go sample acquisition mechanism, or TAGSAM. The mission also had planetary defense implications — as a near-Earth asteroid, Bennu has a small chance of hitting the planet in the next century.
Bennu is, as the space crow flies, about 200 million miles (321 million km) away; OSIRIS-REx arrived two years after launch. On Oct. 20, 2020, the truck-sized spacecraft sampled the young, 60-foot-wide (18 m) crater area Nightingale. Dust and pebbles were blown about as OSIRIS-REx touched down; the TAGSAM itself blew nitrogen gas at the surface to usher material into the sample container. Contact pads on the sampling arm also collected tiny particles before the craft backed off.
Ultimately, Lauretta says, the TAGSAM’s robotic arm actually went into the asteroid some 20 inches (50 centimeters), up to its elbow joint, packing the sample mechanism and initially jamming the closure flap with a rock just 1.2 inches (3 cm) wide. The team was able to stow the sample in the return capsule a week later.
In spring 2021, OSIRIS-REx’s engines burned for home. Earlier this month, the craft first made a final Earth-targeting burn, along with a later small course correction, bringing it into position to release the capsule for re-entry.
Later, Lauretta called the landing “pulse-pounding. Boy, did we stick that landing! It didn’t move, it didn’t roll, it didn’t bounce.” He says that during re-entry, the entire sample could have been jostled so much that “it could all be powder” by the time it landed — though that won’t affect researchers’ ability to analyze the materials. More will be known soon but he joked that his curation team “wouldn’t let me shake it.”
Precious cargo
About 1/3 mile (0.5 km) in diameter, Bennu is a carbonaceous asteroid that has changed little in 4.5 billion years. Meteorites from carbonaceous asteroids are rare and valuable, containing organic molecules, hydrocarbons and amino acids — elements necessary for life as we know it. Some even have water.
Asteroid Bennu, imaged from 15 miles (24 kilometers) away. Credit: NASA/Goddard/University of Arizona
Bennu’s samples will be even more pristine than those in meteorites. That’s because the material won’t have traveled through Earth’s atmosphere unprotected nor landed exposed on the surface our of world, open to the elements for potentially years before discovery and retrieval.
OSIRIS-REx has now given us the largest sample returned from a body beyond the Moon, according to NASA planetary scientist Melissa Morris. The sample will take us “back to the dawn of the solar system,” says Lauretta, noting its material contains the “seeds of life” and will help illuminate how prebiotic chemistry eventually got us to life on Earth.
Lauretta thinks Bennu is about 10 percent water (not liquid but locked up in rock), along with 5 percent carbon by weight. He stresses there’s a “vanishingly small probability” there’s biotic material. But the sample could show the state that occurs between an organic molecule and life itself.
Lauretta and others are particularly keen on the record of Bennu’s parent body, which formed only a few million years after the origin of the solar system. That parent body had hydrothermal deposits like those of Earth’s deep-ocean environments, according to Lauretta. Its water helped form such substances as clay. It might also have formed long-chain organic molecules, including amino acids, which are vital for the formation of peptides. In all the meteorites collected on Earth, only one, Lauretta says, has “a hint” of a simple peptide.
It would be a stunning first if the sample material yields such a discovery. Danny Glavin, Senior Scientist for Sample Return at NASA’s Goddard Space Flight Center, says he and his team will be looking for just that long shot. “It’s one of the first things to look for,” he says, adding, “we’re going to go after them hard.”
Asteroid Autumn
Now the OSIRIS-APEX for Apophis Explorer, the mission is heading to that asteroid for a 2029 rendezvous. The 1,200-foot (370 m) world will come within 20,000 miles (32,000 km) of Earth that year, and researchers hope to study how Apophis might be perturbed by the encounter. The team also plans on using the spacecraft’s thrusters to blow material from the surface to study with onboard instruments.
The golden age of asteroid research seems to be upon us. Two Japanese missions have previously retrieved asteroid samples, though not from a carbonaceous world like Bennu. The DART mission successfully demonstrated planetary defense techniques by moving an asteroid’s orbit. Psyche will launch later this year on a mission to a metallic asteroid, and NEO Surveyor, scheduled to launch in 2028, will hunt from space for potentially hazardous asteroids.
With the Bennu sample return and the upcoming the Psyche launch and Lucy flyby of Dinkinesh, NASA is calling this season “Asteroid Autumn.”
For Lauretta, this autumn is both busy and full of relief. He cried when the main chutes deployed, especially since it was not clear that the drogue chutes had opened first. Soon, he will get to analyze the samples, which NASA says will be safely protected in the event of a government shutdown.
But first: a mission celebration party in Tucson. “We’re going to throw down,” he says.
