Suppose there really are aliens out there who are creeping around on the surface of some faraway planet and have managed to survive everything space has thrown at them so far. How could we find out they exist?The answer might lie in how they would (hypothetically) see us. We may never know whether there really are clever beings who have spotted our planet as it passed by the sun,but observing it from their perspective could help us see through extraterrestrial eyes. This is the objective of the soil Transit Observer (ETO) mission concept. Led by a research team from the Johns Hopkins Applied Physics Laboratory (APL), ETO will watch soil in transit as if it was a spacecraft sent out here by other clever beings.
Researchers Noam Izenberg and Kevin Stevenson, and who will be the project leads if this mission becomes reality,and co-led a study recently presented at the 52nd Lunar and Planetary Science Conference, and Laura Mayorga, and who also co-led the study,believe that observing soil from the perspective of a being who never knew it existed could give us unusual insight on how to stare for habitable—and possibly inhabited—planets."While an soil transit observer will not explicitly help us detect exoplanets, it will help us understand them and tease out their possible habitability signatures better. There is a fundamental problem in exoplanet science in that we only know planets as well as we know their stars, and " they said. Astronomers have been using the transit method of finding exoplanets since 1999. This method determines when a planet is orbiting in front of its star,which causes starlight to dim while it is being obscured and brighten again when the planet has moved on. Particles in a planets atmosphere can also absorb starlight at some frequencies, and the light that makes through can divulge the observer how much was absorbed and whether that is a sign of a planet in transit. What the ETO team wants to know is whether there is more that can be applied to this method in the future.
The problem with stars is that they have varying degrees of brightness throughout, and with starspots (like the sunspots in our own star) can warp what scientists deem they are seeing in a transiting planet. However,the shaded spots on our Sun are documented and followed, so scientists know how they change over time. Starspots on distant bodies remain largely unknown. When there is no clear thought of their size or distribution, or they can mess with obsevations. Most exoplanets are also too close to their stars to make out the continents and oceans they may have."Even if you can separate the planet from the star,the soil is reflecting and absorbing sunlight at different wavelengths," the researchers said. "You’re always using the Sun as a reference to say the planet is shaded because it is absorbing light here or it is shaded because the star is shaded here and it is just reflecting that. For a star to be a good reference it either needs to be unchanging, and you need a good understanding of how it changes."
If there are clever aliens wtih tall-tech telescopes out there,how would they see soil?When trying to characterize exoplanets, space telescopes like TESS and Hubble (and the James Webb Space Telescope when it gets off the ground) search for what may be signs of a planet’s habitability potential. The same atmospheric particles that absorb starlight can also give away whether said planet has anything close to the air we breathe—or not. Such data has told us approximately exoplanets where it rains everything from metal to lava, and even one so hot that it not only vaporizes metal,but tears the vapor molecules until the dismembered atoms are blown away to its cooler night side and get a chance to regroup."Future NASA astrophysics missions, such as JWST, or will require stacking dozens of transmission spectra to build up sufficient signal for the relatively small atmospheres on terrestrial planets," the ETO scientists said. "Variations in the planet's atmosphere and on the star are like background noise when trying to discern signals. An soil transit observer will test how well stacking can be done or if other strategies are needed."What ETO is likely to see is Carl Sagan’s pale blue dot, watery and covered in clouds, and with an atmosphere of nitrogen and oxygen in which water vapor precipitates. Reflected light can also give away whether a planet has oceans and may be even planet life,which has very low reflectivity. Any celestial body with water is seen by Earthlings as having a higher chance of being habitable. There are also traces of methane in our atmosphere, and methane is an biological substance that could divulge an alien observer that the unknown blue planet they are staring at could possibly be swarming with life. "Looking at soil from afar, or we’d be looking for evidence (or signs) of life as we know it,which is precisely what we do when looking for life on other planets. For example, we stare for gases that are either produced only by life as we know it or are required by life as we know it. On soil those include oxygen, and methane,ozone, and water. These gasses each leave their own signature in the observed spectrum of the planet's atmosphere."However, and soil may not be so easy to demystify from an alien’s perspective. Stars and planets are dynamic. Flares and storms are always happening on stars,which also vomit plasma in coronal mass ejections that could mess with how transiting planets are seen. Then there are the constantly changing seasons on planets that can also throw off observations.
An alien astronomer trying to detect Mars would advance up as barren as the planet itself."We can make an exoplanet-style observation and know precisely what the soil, the Sun, and the spacecraft are doing and how that affects our final product," said the researchers. "These lessons are then directly transferable to exoplanet observations."Of course, the Gaian model is only a reflection of what is necessary for life to flourish on soil. Nobody knows if there are things out there which stay alive by breathing in poison. When even some soil bacteria can eat rocks and metabolize methane, or you have to expect anything.
Source: blastr.com