Page 1051 | Astronomy Magazine

Mars Express maps aurorae on the Red Planet

An artist’s impression of how the ‘green’ aurorae may look to an observer orbiting on the night-side of Mars.

ESA/M. Holmström (IRF)

November 21, 2008
Scientists using the European Space Agency’s Mars Express have produced the first crude map of aurorae on Mars. These displays of ultraviolet light appear to be located close to the residual magnetic fields generated by Mars’ crustal rocks. They highlight a number of mysteries about the way Mars interacts with electrically charged particles originating from the Sun.

Mars Express’ Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM) — the ultraviolet and infrared atmospheric spectrometer — discovered the planet’s aurorae in 2004.

Now Francois Leblanc, from the Service d’Aeronomie, France, and colleagues have announced the results of coordinated observation campaigns using SPICAM, the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), and the Analyser of Space Plasmas and Energetic Atoms (ASPERA).

They observed nine new auroral emission events that allow them to make the first crude map of auroral activity on Mars. They see that the aurorae seem to be located near regions where the martian magnetic field is the strongest. MARSIS previously had observed higher-than-expected electrons in similar regions. This suggests that the magnetic fields help to create the aurorae.

On Earth, aurorae are more commonly known as the northern and southern lights. They are confined to the polar regions and shine brightly at visible as well as ultraviolet wavelengths. Similar aurorae exist on the giant planets of the solar system. They occur wherever a planet’s magnetic field channels electrically charged particles into the atmosphere.

In all of these planets, the magnetic fields are large-scale structures generated deep in the planet’s interior. Mars lacks such a large-scale internal mechanism. Instead, it just generates small pockets of magnetism where areas of rocks in the martian crust are magnetic. This results in many magnetic pole-type regions all over the planet.

Charged particles, likely electrons in this case, collide with molecules in the atmosphere and produce aurorae. The electrons almost certainly come from the Sun, which constantly blows out electrically charged particles into space. Known as the solar wind, this stream of particles provides the source of electrons to generate the aurorae, as the MARSIS and ASPERA results suggest.

But how the electrons are accelerated to sufficiently high energies to spark aurorae on Mars remains a mystery. “It may be that magnetic fields on Mars connect with the solar wind, providing a road for the electrons to travel along,” says Leblanc.

Any future astronauts expecting a spectacular light show, similar to aurorae on Earth, may be in for a disappointment. “We’re not sure whether the aurorae will be bright enough to be observed at visible wavelengths,” says Leblanc.

The molecules responsible for the visible light show on Earth — molecular and atomic oxygen and molecular nitrogen — are not abundant enough in the martian atmosphere. SPICAM is designed to work at ultraviolet wavelengths and cannot see whether visible light is being emitted as well.

Nevertheless, there is plenty of work for the scientists to do.

“There’s now a large domain of physics that we have to explore in order to understand the aurorae on Mars. Thanks to Mars Express we have a lot of very good measurements to work with,” said Leblanc.

NASA spacecraft detects buried glaciers on Mars

Artist concept of glacier on Mars.

NASA/JPL

November 21, 2008
NASA’s Mars Reconnaissance Orbiter has revealed vast martian glaciers of water ice under protective blankets of rocky debris at much lower latitudes than any ice previously identified on the Red Planet.

Scientists analyzed data from the spacecraft’s ground-penetrating radar and discovered that buried glaciers extend for dozens of miles from the edges of mountains or cliffs. The group reported the results in the November 21 issue of the journal Science. A layer of rocky debris blanketing the ice may have preserved the underground glaciers as remnants from an ice sheet that covered middle latitudes during a past ice age. This discovery is similar to massive ice glaciers that have been detected under rocky coverings in Antarctica.

“Altogether, these glaciers almost certainly represent the largest reservoir of water ice on Mars that is not in the polar caps,” said John W. Holt of the University of Texas at Austin, who is lead author of the report. “Just one of the features we examined is three times larger than the city of Los Angeles and up to half a mile thick. And there are many more. In addition to their scientific value, they could be a source of water to support future exploration of Mars.”

Scientists have been puzzled by what are known as aprons — gently sloping areas containing rocky deposits at the bases of taller geographical features — since NASA’s Viking orbiters first observed them on the martian surface in the 1970s. One theory suggests the aprons are flows of rocky debris lubricated by a small amount ice. Now, the shallow radar instrument on the Mars Reconnaissance Orbiter has provided scientists an answer to this martian puzzle.

“These results are the smoking gun pointing to the presence of large amounts of water ice at these latitudes,” said Ali Safaeinili, a shallow radar instruments team member with NASA’s Jet Propulsion Laboratory in Pasadena, California.

The spacecraft received radar echoes that indicate radio waves pass through the aprons and reflect off a deeper surface below without significant loss in strength. That is expected if the apron areas are composed of thick ice under a relatively thin covering. The radar does not detect reflections from the interior of these deposits as would occur if they contained significant rock debris. The apparent velocity of radio waves passing through the apron is consistent with a composition of water ice.

Scientists developed the orbiter’s shallow radar instrument to examine these mid-latitude geographical features and layered deposits at the martian poles. The Italian Space Agency provided the device.

“We developed the instrument so it could operate on this kind of terrain,” said Roberto Seu, leader of the instrument science team at the University of Rome La Sapienza in Italy. “It is now a priority to observe other examples of these aprons to determine whether they are also ice.”

Holt and 11 co-authors report the buried glaciers lie in the Hellas Basin region of Mars’ southern hemisphere. The radar also has detected similar-appearing aprons extending from cliffs in the northern hemisphere.

“There’s an even larger volume of water ice in the northern deposits,” said JPL geologist Jeffrey J. Plaut, who will publish results about these deposits in the American Geophysical Union’s Geophysical Research Letters. “The fact these features are in the same latitude bands, about 35 to 60 degrees in both hemispheres, points to a climate-driven mechanism for explaining how they got there.”

The rocky debris blanket topping the glaciers apparently has protected the ice from vaporizing, which would happen if it were exposed to the atmosphere at these latitudes.

“A key question is, how did the ice get there in the first place?” said James W. Head of Brown University in Providence, Rhode Island. “The tilt of Mars’ spin axis sometimes gets much greater than it is now. Climate modeling tells us ice sheets could cover mid-latitude regions of Mars during those high-tilt periods. The buried glaciers make sense as preserved fragments from an ice age millions of years ago. On Earth, such buried glacial ice in Antarctica preserves the record of traces of ancient organisms and past climate history.”

Hubble resolves puzzle about loner starburst

NGC 1569 is a dwarf irregular galaxy in the constellation Camelopardalis, 11 million light-years away.

NASA/ESA/STScI/AURA

November 21, 2008
NASA’s Hubble Space Telescope has helped astronomers solve the mystery of the loner starburst galaxy, NGC 1569, by showing that it is one and a half times farther away than astronomers thought.

The extra distance places the galaxy in the middle of a group of about 10 galaxies centered on the spiral galaxy IC 342. Gravitational interactions among the group’s galaxies may be compressing gas in NGC 1569 and igniting the star-birthing frenzy.

“Now the starburst activity seen in NGC 1569 makes sense, because the galaxy is probably interacting with other galaxies in the group,” said the study’s leader, Alessandra Aloisi of the Space Telescope Science Institute (STScI) in Baltimore, and the European Space Agency. “Those interactions are probably fueling the star birth.”

The farther distance means the galaxy is brighter and is producing stars two times faster than first thought. The galaxy forms stars at a rate more than 100 times higher than the Milky Way. This high star-formation rate has remained almost continuous for the past 100 million years.

William Herschel discovered NGC 1569 in 1788. The galaxy is home to three of the most massive star clusters ever discovered in the local universe. Each cluster contains more than a million stars.

“This is a prime example of the type of massive starbursts that drives the evolution of galaxies in the distant and young universe,” said team member Roeland van der Marel of the STScI. “Starburst galaxies can only be studied in detail in the nearby universe, where they are much rarer. Hubble observations of our galactic neighborhood, including this study, are helping astronomers put together a complete picture of the galaxies in our local universe. Put the puzzle pieces in the right place, as for NGC 1569, and the picture makes much more sense.”

Aloisi and her team actually discovered the new distance by accident. They were using Hubble’s Advanced Camera for Surveys to hunt in NGC 1569 for the kind of red giant stars (stars near the ends of their lives) that shine because of fusion of helium nuclei in their cores. These stars are dimmer than bright red giants without helium burning, but, when detected, they can be used to estimate the galaxy’s age.

“When we found no obvious trace of them, we suspected that the galaxy was farther away than originally believed,” said Aaron Grocholski of the STScI and the lead author on a paper describing the results. “We could only see the brightest red giant stars, but we were able to use these stars to recalibrate the galaxy’s distance.” Bright red giants are reliable “standard candles” for measuring distance because they all shine at the same brightness. Once astronomers know a star’s true brightness, they can calculate its distance from Earth.

Previous estimates of the galaxy’s distance made with ground-based telescopes were unreliable because they looked at the galaxy’s crowded core and couldn’t resolve individual red giant stars.

The Hubble study observed both the galaxy’s cluttered core and its sparsely populated outer fringes. The sharpness of Hubble’s Advanced Camera pinpointed individual red giants, which led to a precise distance to the galaxy. Astronomers measured the galaxy’s distance at nearly 11 million light-years away, about 4 million light-years farther than the old distance.

“This was a serendipitous discovery,” Aloisi said. “Hubble didn’t go deep enough to see the faintest red giant stars we were hunting for because the galaxy is farther away than we thought. However, by capturing the entire population of the brightest red giant stars, we were able to calculate a precise distance to NGC 1569 and resolve the puzzle about the galaxy’s extreme starburst activity.”

Scientists discover new planet

The mirror of the 9.2-meter Hobby-Eberly Telescope is visible through the open louvers in this twilight view. In daylight, the flagpoles on the right show the flags of the five HET partner institutions.

McDonald Observatory, University of Texas, Austin

November 20, 2008
A team of astronomers from Penn State University and Nicolaus Copernicus University in Poland has discovered a new planet that is closely orbiting a red-giant star, HD 102272, which is much more evolved than our own Sun. The planet has a mass that is nearly 6 times that of Jupiter, the largest planet in our solar system. The team includes Alexander Wolszczan, the discoverer of the first planets ever found outside our solar system and an Evan Pugh professor of astronomy and astrophysics and the director of the Center for Exoplanets and Habitable Worlds at Penn State; and Andrzej Niedzielski, who leads his collaborators in Poland. The team suspects that a second planet may be orbiting HD 102272, as well. The findings, which will be published in a future issue of The Astrophysical Journal, shed light on the ways in which aging stars can influence nearby planets.

Scientists already know that stars expand as they age and that they eventually may gobble up adjacent planets. In fact, they expect the Sun will swallow Earth in about a billion years. But what scientists don’t yet understand fully is how aging stars influence nearby planets before they are destroyed. The team’s newly discovered planet is interesting because it is located closer to a red-giant star than any other known planet. From the distance of 0.6 astronomical units, which is less than the distance between Venus and the Sun, the steadily expanding giant appears in the planet’s alien skies as a huge reddish disk that is more than 16 times larger than the face of Earth’s Full Moon as it appears to us.

“When red-giant stars expand, they tend to eat up the nearby planets,” said Wolszczan. “Although the planet we discovered conceivably could be closer to the star without being harmed by it, there appears to be a zone of avoidance around such stars. Our discovery pushes it back to about 0.6 astronomical units, which is the size of the new planet’s orbit. It is important to find out why planets don’t want to get any closer to stars, so one of our next steps is to try to figure out why this zone of avoidance exists and whether it occurs around all red-giant stars.”

The team used the Hobby-Eberly Telescope of McDonald Observatory in southwestern Texas to make its discovery. Through the telescope, which is equipped with a precise spectrograph, the scientists observed a pattern of alternating shifts of spectral lines in the light coming from the star, which are located 1,200 light-years from Earth in the constellation Leo. These tiny alternating shifts represent the fingerprint of a star that is moving alternately toward and away from Earth as it wobbles in space responding to the gravitational pull of an orbiting planet. Because of the Doppler effect, the light from the star becomes bluer as it moves toward Earth and then redder as it recedes from it, which is reflected by the measured shifts of the spectral lines. The specific pattern of these shifts, which the research team observed, allowed the scientists to determine that one planet — and possibly two planets — orbit the star. If the second planet exists, the system would become the first multi-planet system discovered around a red-giant star.

Wolszczan said that he is particularly interested in applying to our own solar system the knowledge he gains about the effects of aging stars on planets orbiting other stars. “Our own Sun one day will become a red giant, and it is interesting to think about what will happen to the outer planets of our solar system as the Sun expands,” he said. “For example, Europa, one of Jupiter’s moons, is covered by ice, but if it were to exist closer to the Sun, it might become a warm ocean world that could possibly support life.”

In 1992, Wolszczan became the first person to discover planets outside our solar system when he used the 1,000-foot Arecibo radio telescope to detect three planets orbiting a rapidly spinning neutron star. The discovery opened the door to the current intense era of planet hunting by suggesting that planet formation could be quite common throughout the universe and that planets can form around different types of stellar objects. The Penn State Center for Exoplanets and Habitable Worlds, which Wolszczan directs, fosters research in the field of extrasolar-planet studies in which the primary goals are to find planets where living organisms exist, or might exist, and to determine their rate of occurrence in the universe. The researchers received support from the Polish Ministry of Science and Higher Education, the NASA Astrobiology Program, the Foundation for Polish Science, and the Polish Academy of Sciences.

NASA and DOE collaborate on dark energy research

A slice through the structure of the universe.

NASA

November 20, 2008
NASA and the U.S. Department of Energy (DOE) have signed a memorandum of understanding for the implementation of the Joint Dark Energy Mission (JDEM). The mission will feature the first space-based observatory designed specifically to understand the nature of dark energy.

Dark energy is a form of energy that pervades and dominates the universe. The mission will measure with high precision the universe’s expansion rate and growth structure. Data from the mission could help scientists determine the properties of dark energy, fundamentally advancing physics and astronomy.

“Understanding the nature of dark energy is the biggest challenge in physics and astronomy today,” said Jon Morse, director of astrophysics at NASA headquarters in Washington. “JDEM will be a unique and major contributor in our quest to understand dark energy and how it has shaped the universe in which we live.”

One of the most significant scientific findings in the last decade is that the expansion of the universe is accelerating. The acceleration is caused by a previously unknown dark energy that makes up approximately 70 percent of the total mass energy content of the universe. This mission has the potential to clarify the properties of this mass energy. JDEM also will provide scientists with detailed information for understanding how galaxies form and acquire their mass.

“DOE and NASA have complementary ongoing research into the nature of dark energy and complementary capabilities to build JDEM, so it is wonderful that our agencies have teamed for the implementation of this mission,” said Dennis Kovar, associate director of the DOE Office of Science for High Energy Physics.

In 2006, NASA and DOE jointly funded a National Research Council study by the Beyond Einstein Program Assessment Committee to assist NASA in determining the highest priority of the five proposed missions in its Beyond Einstein program. In September 2007, the committee released its report and noted that JDEM will set the standard in precisely determining the distribution of dark energy in the distant universe. The committee recommended that JDEM be the first of NASA’s Beyond Einstein missions to be developed and launched. Following the committee’s report, NASA and DOE agreed to proceed with JDEM.

Mysterious source of high-energy cosmic radiation discovered

During 10 years, five high-energy cosmic rays (plotted as orange asterisks) came from one small part of the sky near the star Merak in the Big Dipper. Astrophysicists suspect their source is a merging pair of galaxy clusters (blue). Progressively more distant galaxy clusters appear in light blue, green, and red, while the gray shading shows the positional error for each of the five cosmic-ray detections.

G. R. Farrar/A. A. Berlind/D. W. Hogg (New York University)

November 19, 2008
Scientists have discovered a previously unidentified nearby source of high-energy cosmic rays. The finding was made with a NASA-funded balloon-borne instrument floating high over Antarctica.

Researchers from the Advanced Thin Ionization Calorimeter (ATIC) collaboration, led by scientists at Louisiana State University at Baton Rouge, published the results in the November 20 issue of the journal Nature. The new results show an unexpected surplus of cosmic ray electrons at very high energy &#8212 300-800 billion electron volts &#8212 that must come from a previously unidentified source or from the annihilation of exotic theoretical particles used to explain dark matter.

“This electron excess cannot be explained by the standard model of cosmic ray origin,” said John P. Wefel, ATIC project principal investigator and a professor at Louisiana State. “There must be another source relatively near us that is producing these additional particles.”

According to the research, this source would need to be within about 3,000 light-years of the Sun. It could be an exotic object such as a pulsar, mini-quasar, supernova remnant, or an intermediate-mass black hole.

“Cosmic-ray electrons lose energy during their journey through the galaxy,” said Jim Adams, ATIC research lead at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “These losses increase with the energy of the electrons. At the energies measured by our instrument, these energy losses suppress the flow of particles from distant sources, which helps nearby sources stand out.”

The scientists point out, however, that there are few such objects close to our solar system.

“These results may be the first indication of a very interesting object near our solar system waiting to be studied by other instruments,” Wefel said.

An alternative explanation is that the high-energy electron surplus might result from the annihilation of very exotic particles put forward to explain dark matter. In recent decades, scientists have learned that the kind of material making up the universe around us only accounts for about five percent of its mass composition. Close to 70 percent of the universe is composed of dark energy (so called because its nature is unknown). The remaining 25 percent of the mass acts gravitationally just like regular matter, but does little else, so it is normally not visible.

The nature of dark matter is not understood, but several theories that describe how gravity works at very small, quantum distances predict exotic particles that could be good dark matter candidates.

“The annihilation of these exotic particles with each other would produce normal particles such as electrons, positrons, protons, and antiprotons that can be observed by scientists,” said Eun-Suk Seo, ATIC lead at the University of Maryland at College Park.

The 4,300-pound ATIC experiment was designed to be carried to an altitude of about 23.4 miles (37.6 kilometers) above Antarctica using a helium-filled balloon about as large as the interior of the New Orleans Superdome. The goal was to study cosmic rays that otherwise would be absorbed into the atmosphere.

Black holes are the rhythm at the heart of galaxies

This composite image shows M84, a massive elliptical galaxy in the Virgo Cluster, about 55 million light-years from Earth. Hot gas around M84 is shown in a Chandra X-ray Observatory image in blue and a radio image from the Very Large Array is shown in red. A background image from the Sloan Digital Sky Survey is shown in yellow and white.

X-ray: NASA/CXC/MPE/A.Finoguenov, et al; Radio: NSF/NRAO/VLA/ESO/R.A.Laing, et al; Optical: SDSS

November 18, 2008
The powerful black holes at the center of massive galaxies and galaxy clusters act as hearts to the systems. The black holes pump energy out at regular intervals to regulate the growth of the black holes themselves, as well as star formation, according to new data from NASA’s Chandra X-ray Observatory.

Scientists from the University of Michigan, the Max-Planck Institute for Extraterrestrial Physics in Germany, the University of Maryland, Baltimore County (UMBC), the Harvard-Smithsonian Center for Astrophysics, and Jacobs University in Germany contributed to the results.

The gravitational pull of black holes is so strong that not even light can escape from them. Supermassive black holes with masses of more than a billion suns have been detected at the center of large galaxies. The material falling on the black holes causes sporadic or isolated energy bursts. These bursts make black holes capable of influencing their host galaxies’ fate. This new research shows that black holes can pump energy in a gentler and rhythmic fashion, rather then violently.

The scientists observed and simulated how the black hole at the center of elliptical galaxy M84 ends bubbles of hot plasma into space, heating up interstellar space.

This heat is believed to slow both the formation of new stars and the growth of the black hole itself, helping the galaxy remain stable. Interstellar gases only coalesce into new stars when the gas is cool enough. The heating is more efficient at the sites where it is most needed, the scientists say.

Alexis Finoguenov, of UMBC and the Max-Planck Institute for Extraterrestrial Physics in Germany, compares the central black hole to a heart muscle.

“Just like our hearts periodically pump our circulatory systems to keep us alive, black holes give galaxies a vital warm component. They are a careful creation of nature, allowing a galaxy to maintain a fragile equilibrium,” Finoguenov said.

This finding helps explain a decades-long paradox of the existence of large amounts of warm gas around certain galaxies, making them appear bright to the Chandra X-ray Observatory.

“For decades astronomers were puzzled by the presence of the warm gas around these objects. The gas was expected to cool down and form a lot of stars,” said Mateusz Ruszkowski, an assistant professor in the University of Michigan Department of Astronomy.

“Now, we see clear and direct evidence that the heating mechanism of black holes is persistent, producing enough heat to significantly suppress star formation. These plasma bubbles are caused by bursts of energy that happen one after another rather than occasionally, and the direct evidence for such periodic behavior is difficult to find,” said Ruszkowski.

The bubbles form one inside another for a sort of Russian-doll effect that has not been seen before, Ruszkowski said. One of the hot plasma bubbles appears to be bursting and its contents spilling out, further contributing to the heating of the interstellar gas.

“Disturbed gas in old galaxies is seen in many images that NASA’s Chandra X-ray Observatory obtained, but seeing multiple events is really impressive evidence for persistent black-hole activity,” said Christine Jones, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics.

Gamma-ray evidence suggests ancient Mars had oceans

This 3-D map superimposes gamma-ray data from Mars Odyssey’s Gamma-Ray Spectrometer onto topographic data from the laser altimeter onboard the Mars Global Surveyor. The red arrow indicates the shield volcanoes of Elysium rise
in northern Mars, seen obliquely to the southeast. Blue-to-violet colors at the Elysium rise and highlands stretching to the foreground of the map mark areas poor in potassium. Red-to-yellow colors mark potassium-rich sedimentary deposits in lowlands below the Mars Pathfinder landing site (PF) and Viking 1 landing site (V1).

University of Arizona

November 17, 2008
An international team of scientists reports new evidence for the controversial idea that oceans once covered about a third of ancient Mars based on data from the Gamma Ray Spectrometer onboard NASA’s Mars Odyssey.

The orbiter’s Gamma Ray Spectrometer (GRS), controlled by William Boynton of University of Arizona’s (UA) Lunar and Planetary Laboratory, can detect elements buried as much as 13 inches (1/3 meter), below the surface by the gamma rays they emit. That capability led to the instrument’s 2002 discovery of water-ice near the surface throughout much of high-latitude Mars.

“We compared Gamma Ray Spectrometer data on potassium, thorium and iron above and below a shoreline believed to mark an ancient ocean that covered a third of Mars’ surface, and an inner shoreline believed to mark a younger, smaller ocean,” said James M. Dohm, University of Arizona planetary geologist and leader of the international investigation.

“Our investigation posed the question, ‘Might we see a greater concentration of these elements within the ancient shorelines because water and rock containing the elements moved from the highlands to the lowlands, where they eventually ponded as large water bodies?'” Dohm said.

Results from Mars Odyssey and other spacecraft suggest that past watery conditions likely leached, transported, and concentrated such elements as potassium, thorium, and iron, Dohm said. “The regions below and above the two shoreline boundaries are like cookie cutouts that can be compared to the regions above the boundaries, as well as the total region.”

The younger, inner shoreline is evidence that an ocean about 10 times the size of the Mediterranean Sea, or about the size of North America, existed on the northern plains of Mars a few billion years ago. The larger, more ancient shoreline that covered a third of Mars held an ocean about 20 times the size of the Mediterranean, the researchers estimate.

The potassium-thorium-iron enriched areas occur below the older and younger paleo-ocean boundaries with respect to the entire region, they said. The scientists used data from Mars Global Surveyor’s laser altimeter for topographic maps of the regions in their study.

They report their findings in the article, “GRS Evidence and the Possibility of Paleo-oceans on Mars.” The article will be published in a special edition of Planetary and Space Science, which stems from a June 2007 workshop on Mars and its Earth analogs held in Trento, Italy.

Scientific debate on the existence of ancient martian oceans marked by shorelines was sparked by several studies almost 20 years ago. One such study, by Baker and colleagues at the UA Lunar and Planetary Laboratory, proposed that a few billion years ago, erupting magma unleashed floods far greater in volume than Brazil’s Amazon River. The floods ponded in the northern lowlands of Mars, forming seas and lakes that triggered relatively warmer and wetter conditions that lasted tens of thousands of years.

Spacecraft images going back to Mariner 9 in the early 1970s and the Viking orbiters and landers later in the 1970s show widespread evidence for a watery past for Mars. Images and other information from a flotilla of United States and European Mars orbiters have sharpened the details in the past decade. Results from Mars Global Surveyor, Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter highlight a water-and-ice-sculpted martian landscape.

Scientists studying spacecraft images have a hard time confirming “shoreline” landforms, the researchers said, because Mars shorelines would look different from Earth’s shorelines. Earth’s coastal shorelines are largely a direct result of powerful tides caused by gravitational interaction between Earth and the Moon, but Mars lacks a sizable moon. Another difference is that lakes or seas on Mars could have formed largely from giant debris flows and liquefied sediments. Still another difference is that Mars oceans may have been ice-covered, which would prevent wave action.

“The GRS adds key information to the long-standing oceans-on-Mars controversy,” Dohm said. “But the debate is likely to continue well into the future, perhaps even when scientists can finally walk the martian surface with instruments in hand, with a network of smarter spaceborne, airborne, and ground-based robotic systems in their midst.”

XMM-Newton and Integral find clues on magnetic powerhouses

This illustration shows a magnetar.

Sky & Telescope: Gregg Dinderman

November 14, 2008
X-ray and gamma-ray data from the European Space Agency’s (ESA) XMM-Newton and Integral orbiting observatories tested, for the first time, the physical processes that make magnetars, an atypical class of neutron stars, shine in X rays.

Magnetars are different from ordinary neutron stars because their internal magnetic field is thought to be strong enough to twist the stellar crust. Like in a circuit fed by a gigantic battery, this twist produces currents in the form of electron clouds that flow around the star. These currents interact with the radiation coming from the stellar surface, producing X rays.

Until now, scientists could not test their predictions because it is not possible to produce such ultra-strong magnetic fields in laboratories on Earth.

To understand this phenomenon, a team led by Nanda Rea from the University of Amsterdam used XMM-Newton and Integral data to search for these dense electron clouds around all known magnetars, for the first time.

This artist’s impression shows Integral.

ESA

Rea’s team found evidence that large electron currents exist, and it measured the electron density that is a thousand times stronger than in a normal pulsar. The team also measured the typical velocity at which the electron currents flow. With it, scientists have now established a link between an observed phenomenon and an actual physical process, an important clue in understanding these celestial objects.

The team is now working to develop and test more detailed models on the same line to fully understand the behavior of matter under the influence of such strong magnetic fields.

Neutron stars are remnants of massive stars that have collapsed under their own weight on to themselves. Massive stars are 10-50 times as massive as our Sun. Made almost entirely of neutrons (subatomic particles with no electric charge), these stellar corpses concentrate more than the mass of our Sun within a sphere about 12 miles (20 kilometers) in diameter.

They are so compact, a teaspoon of a neutron star would weigh about one hundred million tons. Neutron stars have a strong magnetic field and rotate rapidly.

This artist’s impression shows XMM-Newton.

ESA/C. Carreau

With magnetic fields a thousand times stronger than that of ordinary neutron stars, magnetars are the strongest known magnets in the cosmos.

In comparison, one would need 10 million-million commonly-used hand magnets to generate a comparable magnetic field. Most media used for data storage, for example, would be erased instantly if exposed to a magnetic field a mere million-million times weaker.

So far, about 15 magnetars have been found. Five of them are known as soft gamma repeaters (SGRs) because they sporadically release large, short bursts lasting about 0.1 second of low-energy gamma rays and hard X rays. The other magnetars are associated with anomalous X-ray pulsars (AXPs). Although SGRs and AXPs were first thought to be different objects, we now know that they share many properties and that their activity is sustained by their strong magnetic fields.

NASA tests lunar rovers and oxygen production technology

A prototype drilling rover built by Carnegie Mellon University carries RESOLVE, a small scale soil to oxygen conversion system. Its lunar wheels were developed by Michelin.

NASA

November 14, 2008
NASA has concluded nearly 2 weeks of testing equipment and lunar rover concepts on Hawaii’s volcanic soil. The agency’s In Situ Resource Utilization Project, which studies ways astronauts can use resources found at landing sites, demonstrated how people might prospect for resources on the Moon and make their own oxygen from lunar rocks and soil.

The tests helped NASA gain valuable information about systems that could enable a sustainable and affordable lunar outpost by minimizing the amount of water and oxygen that must be transported from Earth. The Pacific International Space Center for Exploration Systems, known as PISCES and based at the University of Hawaii, Hilo, hosted the trials. Research teams and NASA experts held the tests of several NASA-developed systems in Hawaii because its volcanic soil is similar to regolith, the Moon’s soil.

NASA’s lunar-exploration plan currently projects that on-site lunar resources could generate 1 to 2 metric tons of oxygen annually. This is roughly the amount of oxygen that four to six people living at a lunar outpost might breathe in a year. The field demonstrations in Hawaii showed how lunar materials might be extracted. It also showcased the hydrogen-reduction system used to manufacture oxygen from those materials and how astronauts would store the oxygen. These experiments help engineers and scientists spot complications that might not be obvious in laboratories.

A prototype system combines a polar prospecting rover and a drill designed to penetrate the harsh lunar soil. The rover’s system demonstrates small-scale oxygen production from regolith. A similar rover could search for water ice and volatile gases such as hydrogen, helium, and nitrogen, in the permanently shadowed craters of the Moon’s poles. Carnegie Mellon University of Pittsburgh built the rover that carries equipment known as the Regolith and Environment Science and Oxygen and Lunar Volatile Extraction.

The Cratos rover will deliver lunar regolith to systems that can extract oxygen and other gases from soil. The prototype rover underwent field tests for 2 weeks in Hawaii.

NASA

Larger, complementary systems that might produce oxygen from soil on an outpost-sized scale are known as ROxygen and the Precursor ISRU Lunar Oxygen Testbed (PILOT).

Cratos, a NASA-developed robotic excavator, collected soil for the ROxygen system. Also tested was an excavator Lockheed Martin of Denver developed that uses a bucket drum to collect and deliver soil to PILOT.

Other tested concepts include a new lunar wheel, developed by Michelin North America of Greenville, South Carolina; a lunar sample coring drill, developed for NASA by the Northern Centre for Advanced Technology in Canada; and a night vision camera called TriDAR for the rover’s navigation and drill site selection. Neptec in Canada developed the camera with support from CSA.

Additional instruments that were field tested will be used to improve understanding of minerals found on the Moon. They include a Mossbauer spectrometer from NASA’s Johnson Space Center in Houston and the University of Mainz in Germany; an X-ray diffraction unit called mini CheMIN from NASA’s Ames Research Center at Moffett Field, California, and the Los Alamos National Laboratory in New Mexico; and a handheld Raman spectrometer CSA provided.

CSA also provided a utility support vehicle from Ontario Drive Gear for personnel and hardware transportation on site as well as to evaluate mobility attributes for future human and project-related lunar mobility platforms. Representatives of the German Space Agency demonstrated an autonomous mole drill technology developed for Mars exploration that might be used in future lunar robotic missions.

In addition to tests in laboratories and rock yards, NASA conducts tests at sites around the world known as analogs because they simulate the moonscape and other extreme environments. These analog activities take place in remote field locations where NASA can evaluate the interactions of multiple mission systems relating to mobility, infrastructure, and effectiveness in harsh climates. Hawaii’s volcanic terrain, rock distribution and soil materials provide a high-quality simulation of the Moon’s polar region. Early demonstrations provide valuable information for subsequent hardware and mission concept development.

Mineral kingdom has co-evolved with life

The evolution of organisms with mineralized skeletons, such as this fossil trilobite, had a huge impact on the types of rocks and minerals formed at the Earth’s surface.

Image courtesy Robert Hazen.

November 11, 2008
Robert Hazen and Dominic Papineau of the Carnegie Institution’s Geophysical Laboratory, with six colleagues, reviewed the physical, chemical, and biological processes that gradually transformed about a dozen different primordial minerals in ancient interstellar dust grains to the thousands of mineral species on present-day Earth. (Unlike biological species, each mineral species is defined by its characteristic chemical makeup and crystal structure.)

“It’s a different way of looking at minerals from more traditional approaches,” says Hazen. “Mineral evolution is obviously different from Darwinian evolution — minerals don’t mutate, reproduce or compete like living organisms. But we found both the variety and relative abundances of minerals have changed dramatically over more than 4.5 billion years of Earth’s history.”

All the chemical elements were present from the start in the solar systems’ primordial dust, but they formed comparatively few minerals. Only after large bodies such as the Sun and planets congealed did there exist the extremes of temperature and pressure required to forge a large diversity of mineral species. Many elements were also too dispersed in the original dust clouds to be able to solidify into mineral crystals.

As the solar system took shape through “gravitational clumping” of small, undifferentiated bodies — fragments of which are found today in the form of meteorites — about 60 different minerals made their appearance. Larger, planet-sized bodies, especially those with volcanic activity and bearing significant amounts of water, could have given rise to several hundred new mineral species. Mars and Venus, which Hazen and coworkers estimate to have at least 500 different mineral species in their surface rocks, appear to have reached this stage in their mineral evolution.

However, only on Earth — at least in our solar system — did mineral evolution progress to the next stages. A key factor was the churning of the planet’s interior by plate tectonics, the process that drives the slow shifting continents and ocean basins over geological time. Unique to Earth, plate tectonics created new kinds of physical and chemical environments where minerals could form, and thereby boosted mineral diversity to more than a thousand types.

What ultimately had the biggest impact on mineral evolution, however, was the origin of life, approximately 4 billion years ago. “Of the approximately 4,300 known mineral species on Earth, perhaps two thirds of them are biologically mediated,” says Hazen. “This is principally a consequence of our oxygen-rich atmosphere, which is a product of photosynthesis by microscopic algae.” Many important minerals are oxidized weathering products, including ores of iron, copper, and many
other metals.

Microorganisms and plants also accelerated the production of diverse clay minerals. In the oceans, the evolution of organisms with shells and mineralized skeletons generated thick layered deposits of minerals such as calcite, which would be rare on a lifeless planet.

“For at least 2.5 billion years, and possibly since the emergence of life, Earth’s mineralogy has evolved in parallel with biology,” says Hazen. “One implication of this finding is that remote observations of the mineralogy of other moons and planets may provide crucial evidence for biological influences beyond Earth.”

Stanford University geologist Gary Ernst called the study “breathtaking,” saying “the unique perspective presented in this paper may revolutionize the way Earth scientists regard minerals.”

IBEX spacecraft reaches orbit, begins instrument commissioning

Artist’s impression of IBEX exploring the edge of our solar system.

NASA GSFC.

November 13, 2008
Just more than 3 weeks since its October 19 launch, NASA’s Interstellar Boundary Explorer (IBEX) spacecraft — the first mission designed to image the environment at the edge of the solar system — concluded its orbit-raising phase and is preparing to start science observations.

After its launch to low-Earth orbit (about 140 miles/225 kilometers) onboard a Pegasus rocket, the spacecraft used its solid rocket motor and hydrazine propulsion system to perform a series of burns that ultimately raised its apogee (farthest point from Earth) to about 200,000 miles (322,000 km) and its perigee (closest point) to about 8,000 miles (13,000 km) above Earth — an orbit ideal for its science mission.

“Because the orbit goes so far out — about five-sixths of the way to the Moon — it gets pushed around significantly by lunar gravity and evolves over time in altitude and inclination,” said IBEX Principal Investigator Dr. David McComas, senior executive director of the Space Science and Engineering Division at Southwest Research Institute. “We’re now in an orbit that provides excellent science in viewing.”

Before the science investigation begins, the IBEX team will commission the spacecraft subsystems that weren’t needed for the orbit-raising period as well as the two IBEX science instruments. During commissioning, the spacecraft spin rate will be reduced from 23 revolutions per minute to 4 rpm and pointed toward the Sun. At that point, the remaining subsystems and instruments will be turned on and tuned to ensure optimum mission performance.

When it begins its science observations in early December, IBEX will use energetic neutral-atom imaging to create the first-ever all-sky maps of the interaction between the million miles per hour wind blown out by the Sun and the low-density material between the stars, known as the interstellar medium. The spacecraft will complete an all-sky map of the interstellar boundaries every 6 months.