Extraterrestrial Life Essay, Research Paper

Extraterrestrial life

As biologists learn about life on Earth in all its diversity, and at the rate that new planets are being discovered the search for life elsewhere grows more steadily pressing. We have discovered organisms on the Earth that seem tenacious and tough almost to a fault; they thrive in the most seemingly adverse conditions imaginable, and organisms so fragile and specialized so as to exist in only the most isolated and pristine environments. With the knowledge of this great amount of diversity it is a safe bet that we will one day find organisms in other parts of the galaxy that are not indigenous to the earth. This richness of diverse life though is comprised of creatures that could only survive on the Earth, so in order to draw any strong conclusions life must be found elsewhere. Due to their relative proximity the planets of our own solar system are the best place to start this search. And finally what types of organisms could we expect to find on other planets judging from the samples on earth?

Even with the great diversity of life on earth and new species being discovered almost daily it is unlikely that any terrestrial creatures could survive in the environments of the other planets we have discovered thus far. There is compelling evidence of flowing water on mars and that the moons of Jupiter could contain even vast frozen oceans but these are still unknowns. The other planets we have discovered outside of our solar system all appear to be gas giants similar to the gas giants of our own solar system and these planets and these planets seem like the least likely place to harbor any organisms that we know of. But we must work with the knowledge that we already have and apply the template of life to the rest of the universe since what we have learned of life on earth is all that we know however unlikely it may seem that any of the terrestrial organisms could survive off the earth. We must find organisms on other planets in order to even hazard an educated guess as to what else may be out there.

Life has spread to all corners, and every crack and crevice of the earth, its diversity is staggering. There are tiny worms that live in the Antarctic ice sheets whose metabolisms have slowed to almost a halt giving them life spans far greater than that of most other organisms on the planet. They feed by ingesting organic molecules that are trapped in the ice with them. Then there are the tubeworms that live at the bottom of the ocean, under extreme pressure and in environments that contain almost no molecular oxygen, feeding off the gasses and particles released from magma vents. These extremophiles seem to be the most likely organisms that we would find elsewhere in the galaxy. Their independence from the delicate atmosphere that makes the earth unique is their greatest strength when we assume that organisms similar to these could exist somewhere else in the universe.

When looking to our near neighbor planets the terrestrials look like the best place to find traces of life, and Mars chief among them. The atmosphere of mercury is so thin that it is hard to believe that any organisms could possibly live on the surface. That and extreme temperatures, both cold and hot make this little planet a very unlikely place. Venus also looks like it could be a bit extreme. Due to its runaway greenhouse effect the surface temperature is extremely high, and volatile gases in the atmosphere would kill instantly any known forms of life. Mars, on the other hand has an atmosphere not that different from the Earth, although very cold it is closer to our range than the others. The presence of water ice at the poles is also a good indicator that life may now or in the past have been present. Due to recent discoveries of rivulets on the surface the likelihood of liquid water on or near the surface of the planet has gone up appreciably. Organisms like the ice worms I mentioned before may be able to find a niche in one of the ice caps, or may be there already. Mars is easily the planet of choice among the terrestrials for finding life similar to native earth organisms.

The outer planets are still a mystery to scientists. Although we may know what their upper atmospheres are composed of none of our probes have been able to penetrate deep enough to delve into these planets extensively. These gas giants I have heard referred to as brown dwarfs or nearly stars, due to their enormous mass. It would take a stretch of the imagination to think we could find organisms inhabiting them. The only possibility I have heard of says that organisms could be living in the upper atmosphere of these behemoths, floating around on the torrential winds and not quite deep enough into the atmosphere to be crushed by the pressure and feeding on particles that are in the storm with them.

The moons of the outer planets possibly harbor a much friendlier environment for life to evolve. Titan is one intriguing example. A thick layer of clouds and a possible greenhouse effect obscures the surface. This may sound like not a very amiable mix but due to its distance from the sun this satellite should be very cold, somewhere in the neighborhood of 100K. The greenhouse effect could warm the surface to an acceptable temperature for liquid water to exist and maybe even life. Europa is another of the Galilean satellites that may be hospitable to life, as we know it. It appears to be about 10 to 15% water ice and judging from its spectrum the entire surface looks to be covered by it! With sufficient volcanism below this icy surface there may be an entire ocean of liquid water beneath. This environment could conceivably harbor organisms like the tubeworms mentioned previously.

Judging from the diversity and determination of life on earth I find it almost inconceivable that we will not find life elsewhere in the galaxy, or even in the solar system. Of course our predictive powers would increase greatly if we were to find organisms out there of different composition or different fundamental structure than those on earth, but as yet we haven t. But if Carl Sagan is right (and I believe he is) in stating that there are billions of planets out there then statistics would seem to stand on the side of finding not only a few organisms, but a diversity as great as the universe itself.