Signs of Life

“If alien astronomers are out there searching for signs of life on Earth, they might just find it in the telltale pattern of light reflected by our plants, from redwood forests to desert cacti to grass-covered plains. That reflected fingerprint has been visible since vegetation first began carpeting our rocky terrestrial landscape about half a billion years ago. And as Earth aged and evolution marched onward, the reflected signal strengthened.

“Now, two astronomers are suggesting that plants could leave similar fingerprint-like patterns on distant exoplanets, and perhaps the first signs of life beyond our solar system could come from light reflected by forests covering an alien moon like Endor or cacti living in Tatooine’s deserts.

 
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“We’re trying to figure out—with all the planets we’re finding—what are the signatures that could indicate habitability?” says Cornell University’s Lisa Kaltenegger, who recently described Earth’s leafy signature in a study published in the journal Astrobiology.

“We really want to identify the handful, or two or three, that give us the best chance to pick up signs of life.”

“While this isn’t the first time scientists have suggested looking for life in a far-off planet’s light, Kaltenegger’s team adds a twist: Such reflections can also offer a good estimate for an alien planet’s evolutionary advancement, based on our knowledge of how things work on Earth.

“This idea that you could find vegetation on another planet has been around. But nobody ever used Earth’s own geological history as an archive,” Kaltenegger says. “We don’t have a second planet with habitability, but we do have our Earth through time, and it would be really smart to study it.”

“Several decades ago, the Galileo spacecraft, which was headed for Jupiter, swiveled to stare at Earth’s reflected light. It spied the signs of biology at work in the presence of atmospheric gases such as ozone and methane. More recently, astronomers have teased apart Earthshine, or the bit of Earth-light that sometimes dimly illuminates the darker part of a crescent moon’s face. They found life’s fingerprints there, too.

“Now, scientists searching for life beyond Earth are debating how biology might leave molecular marks in alien atmospheres, either by producing particular compounds or by shifting the mix of gases swaddling a planet.”

Text: “Want to Find Alien Life? Look at Older, Hotter Earths”, National Geographic.
Image: L’occhio di Shui (The Eye of Shui) by Shui Mao.

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The Local Standard of Rest

“Whereas all the planets, asteroids and meteors that originate within the solar system more or less circle what is called the Ecliptic plane, that of our sun, since they were formed from the same disc of gas and dust that rotated around itself, Oumuamua entered the solar system north of the plane, in an extreme hyperbolic orbit and at a speed of 26.3 kilometers per second faster relative to the motion of the sun.

“A reconstruction of its trajectory shows that Oumuamua traversed the ecliptic plane on September 6, 2017, when the sun’s gravity accelerated the object to a velocity of 87.8 kilometers per second. On September 9, the object passed closer to the sun than the orbit of Mercury. And on October 14, five days before it was discovered in Hawaii, the object passed 24.18 million kilometers away from Earth, or 62 times the distance from here to the moon.

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“I wrote above that Oumuamua originated at Vega, but that’s not completely accurate: The universe is a vast place, and even at Oumuamua’s velocity – a velocity that no human spaceship has achieved – a voyage from Vega to the solar system would take 600,000 years. But in the meantime, Vega is orbiting the center of the Milky Way, like the sun and all the other stars, and it wasn’t in that region of the heavens 600,000 years ago.

“If you average the velocities of all the stars in the region, you get a system that’s called the ‘local standard of rest.’ Oumuamua was at rest relative to that system. It didn’t come to us. It waited in place, like a buoy on the surface of the ocean, until the ‘ship’ of the solar system ran into it. To make things clear, only one of 500 stars in the system is as much at rest as Oumuamua. The probability of that is very low. After all, if it were a stone that was simply hurled from a different solar system, we would expect it to have the velocity of its star system, not the average velocity of all the thousands of stars in the vicinity.”

Text: “If True, This Could Be One of the Greatest Discoveries in Human History”, Haaretz.

Image: Augsburger Wunderzeichenbuch, Comet mit einem grosen Schwantz, 1401

Heliocentric Reality

“In the hidden heart of science fiction had always been the hope that the moon and the planets promised some personal adventure akin to [a] sudden encounter with the Pacific – a transitory, enchanted moment when man, like Fitzgerald’s Dutchmen, would hold its breath before the fresh green beast of some radiant new world. At that moment, descending Christlike into time and space, the cosmos would become a place. This was the promise of [Chesley] Bonestell’s beaches – that those peaceful points of light in the night sky were places, that virgin rocks, asleep for a billion years, await my touch no less than the cup that sits before me, that there is a “transcendent mundaneness” abiding in parallel time and space, one that somehow merges the cosmic and the personal. Like the seashore, a Bonestell moonscape is a scared place at the edge of the known world – an altar set before the barrier, a piece of the mundane bathed in oceanic mystery.

“We think of the boundaries of the known, the outer rim of our reality, as somehow harbouring the answers to our “Why” questions. Whether it be Aristotle’s geocentric spheres, Columbus’s ocean-sea, or our own space-time continuum, we conceive of this Larger Context as ultimately separate from an and alien to our everyday experience simply because it is assumed to mask the unknowable, the meaning of all meaning, as inaccessible to us as cosmology to an ant. To encounter the blue skies of Bonestell’s Titan, or to find that the reddish, rock-strewn desert of Mars looks like the American Southwest, suggests that the near edge of the Larger Context is a reality as familiar as my own backyard. Just as the beach is perceived as the edge of infinity out of the abstract and into the realm of direct experience.

“The two realms, abstract and direct, are quite different. In one, red is a designated wavelength of light; in the other, red is a colour. In one, the earth rotates on its axis and revolves about the sun, in the other, the sun rises and sets. The photographic realism of Bonestell’s cosmic beaches brings the two realms together at the point of tangency, allowing one experience to experience the heliocentric reality from a geocentric perspective, giving the Larger Context a tactile immediacy. The paintings had a disorienting effect similar to seeing the earth from the Moon. Standing there under the blue swirl of of Earth, said the astronauts Gene Cernan, “I had to stop and ask myself, ‘Do you really know where you are in space and time and history?'”. To believe, with one foot in each world, that one can retain an earthly reality yet stand on another ground under another sky, has the transforming impact of an out-of-body experience, or an encounter with a Doppelgänger, a duplicate self.”

Text: Wyn Wachhorst. “The Dream of Spaceflight: Nostalgia for a Bygone Future”, The Massachusetts Review, Vol. 36, No. 1 (Spring, 1995), pp. 7-32.

Image Top:  Saturn as seen from Titan, painting by Chesley Bonestell, 1944.

Image Bottom: Huygens Probe, view from Titan’s Surface, 2005. Credit: ESA/NASA/JPL/University of Arizona