Earth's Almost Sibling Found? Kepler 452b
You may have heard recently about the discovery of the most Earth-like planet yet, Kepler 452b. Scientists are calling it Earth's cousin, and it certainly has a lot of characteristics that make it match that description.
|Image: Kepler 452b - Artist's Concept Courtesy NASA|
1,400 light-years away, Kepler 452b sits in its star's habitable zone, what Neil DeGrasse Tyson calls the "Goldilocks Zone." The sun that rises on this world is yellow, like ours (Class G), and Kepler-452b sits in about the same orbit as the Earth does around Sol.
All of this is pretty exciting, including the fact that although 60% larger than the Earth, Kepler-452b is estimated to have only about 2x the gravity. This means that life as we know it wouldn't be so hindered by the planet's gravitational pull. (Any future space travelers would find their weight doubled but it wouldn't kill them).
|Image courtesy NASA|
How does the presence of oxygen mean life as we know it, you ask?
Oxygen is an incredibly unstable molecule. It likes to bond with just about anything it can. Ever watch something rust? See your fine silver tarnish? Wonder why the Statue of Liberty is green and not bronze? Wonder why what lets fire burn? The answer is oxygen. To loosely quote NDT: if all plant life on this planet (and algae) were to suddenly die, the oxygen in the air would slowly be depleted (with or without the presence of living things) as it bonded with the other elements in the environment. Eventually there would be none left in the atmosphere. Things that photosynthesize, like plants and algae and certain types of bacteria, are the only reason why there is oxygen in the air for us to breathe. If we look at an exoplanet's atmosphere and see oxygen (which we can do by analyzing the light passing through it with spectroscopy), we will know that there is life of some kind present.
Personally, I have my fingers crossed for Kepler-452b, but time will tell. The next question after answering whether or not there is oxygen available in the atmosphere (and therefore photosynthesizing life), would be if there are animals as we understand them on the planet. That question is a bit harder to answer, since the major giveaway for animal life (as we understand it) in the atmosphere isn't a perfect test.
Methane is a good indicator that biological processes are going on, but it can also be produced by natural chemical processes that don't involve life (we've found methane on Mars, but we have yet to find signs of life). The same goes for carbon-dioxide, so animal life could be impossible to detect without actually traveling to a planet to physically look and take samples. However, there is one gas that if we found it in an atmosphere, we would definitely know there was animal life:
|Photo by Fidel Gonzales used under Creative Commons license|
The presence of smog would be a dead giveaway that there was life as we know it. As I'm sure you've guessed by now, true smog (vs. the "vog" version produced by volcanoes) only occurs when fossil fuels and other industrial chemicals are burned by "intelligent" life. If we find smog in a planet's atmosphere, we would finally have the answer to the question of "are we alone?"