We will begin here at home, on Earth. The Earth contains a plethora of millions of different species specially adapted for their environments. What features do they all share in common? What could a termite gnawing on a piece of wood possibly have in common with you, a human, sitting there reading this paper? Getting through the obvious physical differences, chemically all life here on Earth is related. All life, as we know it, contains certain elements that make up many of the biomolecules that we consider vital for life to exist. The six most important elements have the acronym CHNOPS, standing for: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur. These elements are exceptionally common in space, particularly in carbonaceous(C- type) asteroids. C-type asteroids are the most common variety, making up about 75% of all known asteroids. They frequently come in from the outer asteroid belt and collide with the Earth. Such collisions were especially common early in Earth's history and these impactors may have been crucial in the formation of the planet's vast oceans. This has led some scientists to the hypothesis of panspermia, which states that life exists throughout the universe and is distributed by asteroids, comets, and planetoids. Meaning life could have been initially seeded by early impactors. If the Earth could have been initially seeded by life that begs the question of whether other worlds could have been as well.
Space is a very harsh place: bitter cold, crushing atmospheres, extreme radiation, and varying degrees of gravitational pull. Organisms would have to survive conditions that, at least at first glance, seem impossible for life to exist. Is that all-together true, or could life be more resilient than you think? The answer is yes. Here on Earth we house a myriad of specialized organisms that can survive just the conditions I stated above; we call them extremophiles. Most extremophiles fall within the domain of Archea and are capable of living where, until very recently, life was said to be impossible. There are many classes of extremophiles that range all around the globe, each corresponding to the way its environmental niche differs from normal conditions. Could organisms similar to extremophiles live on other planets? For example, Mars may have regions in its deep subsurface permafrost that could harbor Endolith communities. Endolith are extremophiles that live in microscopic spaces within rocks. The subsurface water ocean of Jupiter's moon, Europa, may harbor life as well, especially at hypothesized hydrothermal vents at the ocean floor. Nature has a way of continually surprising us; where we think life couldn’t possibly be, we find it is brimming with all sorts of unique creatures. Future generations may one day look back and think of how ignorant we were thinking life was confined to our blue green planet.
The chemistry necessary for life on our planet is present in space; all it needs is a place where life can grow, live, and persist. Could that place be found in our own cosmic backyard? We have sent dozens of probes to the other celestial bodies that orbit with us around the sun that have brought back treasure troves of information. Mars being the most Earth-like, and significantly closer has received more attention than any of the other planets as a candidate for housing life. Evidence has shown that Mars once had running water, but something in its planetary history caused the water to freeze up in the polar ice caps trapping much of its atmosphere. In the 1970s, NASA sent two different spacecraft to Mars as part of the Viking program. Viking’s mission was to perform four different types of biological experiments to detect any bio-signatures left by life. Sadly, the results of these experiments were inconclusive, and sparked controversy over the results. One of Viking’s greatest limitations was its lack of mobility. Viking could only analyze what was within the range of its arm. With advances in technology mobile labs or “rovers” were created as a solution to the problem. Since then, rovers have become the best way of scrutinizing the red Martian surface. Currently we have an active rover mission called the Mars Science Laboratory, or Curiosity. The overall objectives include investigating Mars' habitability, studying its climate and geology, and collecting data for a manned mission to Mars.
The Jovian moons have played a significant role in the history of science. When Galileo Galilei in 1610 looked through his telescope at Jupiter he noticed that three “stars” seemed to be orbiting it. This single, innocent, act proved without a doubt that the Earth could not be the center of the universe. The planets orbited the sun, contradicting the widely held belief of geocentrism. Those “stars” that Galileo saw were actually the moons of Jupiter. Europa is one of those moons, and is of particular interest of astrobiologist today. Scientist hypothesize that underneath Europa’s smooth icy surface is a vast liquid ocean of water kept warm by tidal heating from the gravitational pull of Jupiter and Io (another Jovian moon). Recently, science has discovered a potential energy source for life. "Life as we know it needs liquid water, elements like carbon, nitrogen, phosphorus and sulfur, and it needs some form of chemical or light energy to get the business of life done," study leader Kevin Hand, of NASA's Jet Propulsion Laboratory. It seems odd but the deadly chemical Hydrogen peroxide may be that energy needed to get life started. If the hydrogen peroxide finds a way beneath Europa's surface and mixes with the moon's liquid water ocean, it could be a vital energy source for any life that might exist there.
In 2005, as the Cassini- Huygens Probe was passing Saturn Huygens descended down to the surface Saturn’s largest moon, Titan. The pictures that Huygens sent back to Earth are striking to their similarity to the shallow tide pools of our home planet. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found. Titan’s dense atmosphere, like Earths’, is composed mostly of nitrogen. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes and seas of liquid methane and ethane. From Titan the Sun is a tiny pinhole of light against a dark background. Could these stable liquid lakes be the birth place of some exotic life or is it far too cold for biological processes to occur? A life form similar to the cyrophiles on Earth (an extremely cold resistant extremophile) may be able to survive the cold.
If life on Earth has taught us anything, it’s that life is resilient and will be found in the least likely of places. We may not have found evidence for life yet, but this gives the human species something to wonder about and work towards. Knowing that out there in the vast cosmic darkness there may be other beings looking up at the night sky asking the same questions we are, is an exciting prospect in itself. The universe is so vast and diverse that the likelihood of life existing is inevitable. All that is left to do is take the time to look closely enough to find it.
Bibliography
Carl Sagan. The Cosmos.
http://en.wikipedia.org/wiki/Astrobiology
http://en.wikipedia.org/wiki/Panspermia#Objections_to_panspermia_and_exogenesis
http://en.wikipedia.org/wiki/C-type_asteroid
http://en.wikipedia.org/wiki/CHNOPS
http://en.wikipedia.org/wiki/Extremophile
http://astrobiology2.arc.nasa.gov/missions/
https://astrobiology.nasa.gov/about-astrobiology/
http://en.wikipedia.org/wiki/Life_on_Mars_(planet)
http://en.wikipedia.org/wiki/Search_for_Extra-Terrestrial_Intelligence
http://en.wikipedia.org/wiki/Curiosity_rover
http://en.wikipedia.org/wiki/Abiogenesis
http://www.space.com/19157-billions-earth-size-alien-planets-aas221.html
http://www.space.com/20536-jupiter-moon-europa-life-ingredients.html
Space is a very harsh place: bitter cold, crushing atmospheres, extreme radiation, and varying degrees of gravitational pull. Organisms would have to survive conditions that, at least at first glance, seem impossible for life to exist. Is that all-together true, or could life be more resilient than you think? The answer is yes. Here on Earth we house a myriad of specialized organisms that can survive just the conditions I stated above; we call them extremophiles. Most extremophiles fall within the domain of Archea and are capable of living where, until very recently, life was said to be impossible. There are many classes of extremophiles that range all around the globe, each corresponding to the way its environmental niche differs from normal conditions. Could organisms similar to extremophiles live on other planets? For example, Mars may have regions in its deep subsurface permafrost that could harbor Endolith communities. Endolith are extremophiles that live in microscopic spaces within rocks. The subsurface water ocean of Jupiter's moon, Europa, may harbor life as well, especially at hypothesized hydrothermal vents at the ocean floor. Nature has a way of continually surprising us; where we think life couldn’t possibly be, we find it is brimming with all sorts of unique creatures. Future generations may one day look back and think of how ignorant we were thinking life was confined to our blue green planet.
The chemistry necessary for life on our planet is present in space; all it needs is a place where life can grow, live, and persist. Could that place be found in our own cosmic backyard? We have sent dozens of probes to the other celestial bodies that orbit with us around the sun that have brought back treasure troves of information. Mars being the most Earth-like, and significantly closer has received more attention than any of the other planets as a candidate for housing life. Evidence has shown that Mars once had running water, but something in its planetary history caused the water to freeze up in the polar ice caps trapping much of its atmosphere. In the 1970s, NASA sent two different spacecraft to Mars as part of the Viking program. Viking’s mission was to perform four different types of biological experiments to detect any bio-signatures left by life. Sadly, the results of these experiments were inconclusive, and sparked controversy over the results. One of Viking’s greatest limitations was its lack of mobility. Viking could only analyze what was within the range of its arm. With advances in technology mobile labs or “rovers” were created as a solution to the problem. Since then, rovers have become the best way of scrutinizing the red Martian surface. Currently we have an active rover mission called the Mars Science Laboratory, or Curiosity. The overall objectives include investigating Mars' habitability, studying its climate and geology, and collecting data for a manned mission to Mars.
The Jovian moons have played a significant role in the history of science. When Galileo Galilei in 1610 looked through his telescope at Jupiter he noticed that three “stars” seemed to be orbiting it. This single, innocent, act proved without a doubt that the Earth could not be the center of the universe. The planets orbited the sun, contradicting the widely held belief of geocentrism. Those “stars” that Galileo saw were actually the moons of Jupiter. Europa is one of those moons, and is of particular interest of astrobiologist today. Scientist hypothesize that underneath Europa’s smooth icy surface is a vast liquid ocean of water kept warm by tidal heating from the gravitational pull of Jupiter and Io (another Jovian moon). Recently, science has discovered a potential energy source for life. "Life as we know it needs liquid water, elements like carbon, nitrogen, phosphorus and sulfur, and it needs some form of chemical or light energy to get the business of life done," study leader Kevin Hand, of NASA's Jet Propulsion Laboratory. It seems odd but the deadly chemical Hydrogen peroxide may be that energy needed to get life started. If the hydrogen peroxide finds a way beneath Europa's surface and mixes with the moon's liquid water ocean, it could be a vital energy source for any life that might exist there.
In 2005, as the Cassini- Huygens Probe was passing Saturn Huygens descended down to the surface Saturn’s largest moon, Titan. The pictures that Huygens sent back to Earth are striking to their similarity to the shallow tide pools of our home planet. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found. Titan’s dense atmosphere, like Earths’, is composed mostly of nitrogen. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes and seas of liquid methane and ethane. From Titan the Sun is a tiny pinhole of light against a dark background. Could these stable liquid lakes be the birth place of some exotic life or is it far too cold for biological processes to occur? A life form similar to the cyrophiles on Earth (an extremely cold resistant extremophile) may be able to survive the cold.
If life on Earth has taught us anything, it’s that life is resilient and will be found in the least likely of places. We may not have found evidence for life yet, but this gives the human species something to wonder about and work towards. Knowing that out there in the vast cosmic darkness there may be other beings looking up at the night sky asking the same questions we are, is an exciting prospect in itself. The universe is so vast and diverse that the likelihood of life existing is inevitable. All that is left to do is take the time to look closely enough to find it.
Bibliography
Carl Sagan. The Cosmos.
http://en.wikipedia.org/wiki/Astrobiology
http://en.wikipedia.org/wiki/Panspermia#Objections_to_panspermia_and_exogenesis
http://en.wikipedia.org/wiki/C-type_asteroid
http://en.wikipedia.org/wiki/CHNOPS
http://en.wikipedia.org/wiki/Extremophile
http://astrobiology2.arc.nasa.gov/missions/
https://astrobiology.nasa.gov/about-astrobiology/
http://en.wikipedia.org/wiki/Life_on_Mars_(planet)
http://en.wikipedia.org/wiki/Search_for_Extra-Terrestrial_Intelligence
http://en.wikipedia.org/wiki/Curiosity_rover
http://en.wikipedia.org/wiki/Abiogenesis
http://www.space.com/19157-billions-earth-size-alien-planets-aas221.html
http://www.space.com/20536-jupiter-moon-europa-life-ingredients.html