From the May 2011 issue

The smell of space

July 2011: How do our other senses apply to astronomy?
By | Published: May 23, 2011 | Last updated on May 18, 2023
Astronomy is a visual science. All our knowledge begins with photons of light. By stimulating our retinas, they provoke 12 watts of electricity to course through our 1000 cc, motorcycle-cylinder-sized brains. The result: images of various nebulae.

Yet the universe makes us use the poorest facets of our vision. Most backyard astronomers assume the gray galaxies and blurry nebulae they see are due to their modest optics. But as I’ve pointed out before, “blurry and gray” is simply how our eyes perceive faint objects. Galaxies exhibit a low surface brightness through telescopes. In such dim light, the retina’s only tool is its 120 million rod cells, which produce a pathetic 20/200 sharpness and a total absence of color. Observe the Whirlpool Galaxy and you are legally blind — plus as colorblind as an owl. But is vision really our only tool for probing the cosmos? What about our other senses?
Sound: Some folks insist they’ve heard meteors. And a dozen observers in Alaska emphatically told me the aurora they witnessed was accompanied by hisses and crackles. Yet sensitive microphones set up by University of Alaska researchers in Fairbanks have never detected any sound whatsoever. In truth, the large distances (80 miles [130 kilometers] to meteors and even farther to aurorae), plus the very thin air up there, would make sounds virtually impossible. And even then it would require at least 7 minutes for a noise to reach the surface. That’s a far cry from the instantaneous reports.

Call me naïve, but I still believe those people. I think some folks somehow perceive the radio waves generated by meteors as they ionize the air around them. Similarly, aurorae are often accompanied by huge electrical currents on the ground. Such electromagnetic phenomena move at light-speed, so any noises should indeed be simultaneous. Still, how anyone’s senses could perceive this is a mystery.
The biggest boom box in our neck of the woods is the Sun. Its surface has nonstop, complex, up-and-down pulses, like a woofer. Studying those is the province of helioseismology, which is fun to say. It’s a powerful tool for probing what’s below the solar photosphere, just as earthquakes tell us what’s going on beneath our planet’s surface. Those pulses definitely create sounds. If the solar system ever passes through an impossibly dense nebula, we might someday hear the music of the Sun.

No, you don’t want to
go around sniffing
 the solar system.

Smell: To have any smell at all, atoms must cling to our nasal membranes. This is why large molecules like tetracycline or DNA have no odor — they’re too big to stick to our noses. But truly large molecules are rare beyond Earth, so most celestial objects would indeed have some sort of scent. Unfortunately, the universe does not smell like roses. Parts of the solar system generate foul substances. Io’s volcanoes spew out putrid sulfur dioxide. Jupiter’s environment is worse than a college dorm. Uranus and Neptune are rife with ammonia. No, you don’t want to go around sniffing the solar system.

Even the Moon may stink. When Michael Collins received Apollo 11’s samples, the containers had lots of lunar dust on them, which wafted into the command module. Collins said it smelled awful. Then again, maybe he was really getting a whiff of Aldrin’s socks. Or perhaps the Moon is made of green cheese after all, and a government conspiracy is covering this up.

Lunar regolith (soil) is mostly silicon and oxygen, so in theory the Moon should smell like sand. However, trace materials often impart distinctive odors to things, so compounds like iron oxide, which is 12 percent of the Moon, are what probably give it a foul stench.

Touch: Is this a touchy-feely universe? Maybe a little. In addition to the 842 pounds (382 kilograms) of Moon rocks Apollo astronauts carried back, plus 5 ounces (142 grams) the Soviets scooped up and returned robotically, the Stardust mission captured grains of Comet 81P/Wild, which contained the life-friendly amino acid glycine. The allure of “hands on” explains why meteorites are so popular. For a few hundred dollars, you can buy a gorgeous octahedrite. “Here!” you say to guests, letting them hold a heavy black metallic chunk that a magnet will yank. It’s fun to hand someone an asteroid. (Meteor showers are fragile comet ices that never make it to Earth. A meteorite you can touch is an asteroid or a piece of the Moon or Mars.)

You can touch the Moon at Washington’s Air and Space Museum, where a lunar rock is set so you can run your fingers over it. If you could leave Earth and briefly remove your gloves, you’d find the Moon’s surface as pleasantly fine as baby powder, martian soil much coarser to the touch, and Venus rock-hard and nearly red hot. The outer planets have no surfaces at all, so you’d just be swiping at cold gas.

Bottom line: Our non-visual senses offer slim celestial pickings, and they’re not always agreeable. Looks like we’ll stick with those photons. Maybe gray is cool, after all. Noticing the transformation of my mustache, I can only hope so.

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