(4) Life in our backyard
Summary in seconds: no “lots of life” in our solar system, why do we search for life on our neighboring planets, signs of life on Earth as seen from space, and what to expect in our next article.
Searching for life in our solar system, why?
“There’s nothing else in the solar system with lots of life on it,” said Mary Voytek1, senior scientist for astrobiology at NASA. After decades of imagining little green aliens speeding through space in their shiny flying disks, astrobiologists have concluded that there is not much evidence for life in the celestial bodies of our solar system. “lots of life” does not exist in our solar system. Nevertheless, astrobiologists are looking forward to the possibility of finding more primitive life forms2 or the so called “signatures of life”, which I mentioned in my previous article in this series. Finding any trace of life in our back yard (the solar system) will prove that life on earth is not a miracle and that we are not alone in the universe.
Aside from Earth, in our solar system, the conditions on our neighboring rocky planets are either too hot, like Mercury and Venus, or too cold like Mars. As for the rest of the planets, they are giant gaseous masses on which life is inconceivable. Studying various biological manifestations on our planet showed us the ability of life to thrive under the harshest conditions and in the most hostile environments. On the surface of Earth various forms of life are thriving in extremely cold and arid conditions, and in the depth of our oceans under extreme pressure and without sunlight as a source of energy3. The question now is, can life exist in similar or more extreme environments on other extraterrestrial bodies in our solar system.
Our understanding of the solar system has expanded dramatically over the past few years. As a result, we now know that Venus and Mars may have had more habitable ecosystems, and that some form of life may have evolved there before the conditions of these rocky planets took a significant turn for the worth.
The technology that we now have does not give us the ability to explore exoplanets, we must take advantage of our current capabilities to study the nearby planets and moons in our solar system.
Signs of life on Earth as seen from space
Studying signs of life on Earth from space would provide useful guidelines to what life may look like on other extraterrestrial members of our solar system. On the 8th of December 1992, we got a chance to examine what the sole life-bearing world looked like from space4. On that day, the space probe Galileo streaked within 190 miles of Earth as it gained extra charge of energy from our planet’s gravity on its course to Jupiter.
Galileo found multiple signs of life on Earth, like Oxygen and Methane. The probe detected a spike in the infrared part of the light spectrum (the red edge), which is indicative sign of reflective vegetation on the surface of our planet. Galileo even detected a sign of intelligent life. In this case, powerful radio waves that were unlikely to come from natural sources.
Best places for Life in our solar system
The planets and moons of our solar system, are extraordinarily diverse. From charbroiled Mercury and Venus to the frozen outer reaches of the Oort Cloud5 and in between are few celestial bodies with probable potentials for life.
In our solar system, the list of celestial bodies prospects of life, includes two planets. The first planet is Mars which was once temperate and flowing with water, but now is cold, nearly airless and arid desert. But it possesses subterranean potentials for life. The second planet is Venus which, despite its broiling surface, may have life potentials in its high-altitude clouds.
The list, also, includes seven moons, with their hidden oceans, which revolve around three giant gaseous planets: Jupiter (Europa, Ganymede, Calisto, and Io), Saturn (Titan and Enceladus), and Neptune (Triton).
The last celestial candidate for harboring life in our solar system, outside Earth, is the dwarf planet Ceres in the asteroid belt, which astrobiologists speculate harboring a possible “water world” either now or earlier in its history.
Add to that the frozen outer reaches of the Oort Cloud5, with their dwarf planets and would-be comets locked in deep freeze. Their potentials for harboring life may be slim but it can’t be ruled out.
In my next article I will detail the potentials for life and the biosignatures that we may find on each one of these ten celestial bodies of our solar system.
References
1. Mary Voytek: the director of the National Aeronautics and Space Administration (NASA) Astrobiology Program at NASA Headquarters in Washington, D.C.
https://en.wikipedia.org/wiki/Mary_Voytek
2. Life in Our Solar System? Meet the Neighbors
https://exoplanets.nasa.gov/news/1665/life-in-our-solar-system-meet-the-neighbors/
3. The best places to find extraterrestrial life in our solar system
4. Galileo Swinging by Earth
https://www.orlandosentinel.com/news/os-xpm-1992-12-08-9212080234-story.html
5. The Oort Cloud: is a predicted collection of icy objects farther away than everything else in the solar system. It fits with observations of comets in the planetary region of the solar system, but scientists have yet to observe any object in the Oort Cloud itself.