NASA is trying to answer a deeper question: if we ever find alien life in the Universe, as we understand this? Whatever in the cosmos, whatever it is, it can be a truly strange and unrecognizable. When robotic probe to land on a water world like Jupiter's Europe that needs to see the scientists to throw up his hands, slap the table and adjusted his glasses on the bridge of your nose to say: this is life?
This issue is of concern and retired astronaut John Grunsfeld. In any case, this became clear when he answered questions about the scientific missions of the Agency in 2002.
"We looked at him with stone faces," says Jim green, head of planetary science at NASA. "We need to build to do to find life? What tools, what methods, what objects to look for?". The search for life in the first place is the definition of life, and green says that the basic functions that are currently allocated, this metabolism, reproduction and evolution. These signs should show life.
In late December, NASA asked the prestigious National Academy of Sciences, technology and medicine to bring together the leading experts from the field of astrobiology meeting to discuss the current status of the search for extraterrestrial life in the solar system and extrasolar planetary systems.
There is a growing interest in biosignatures or substances that provide proof-of-life — as NASA prepares mission for their potential detection. Among them a visit to Europe in the 2020s, and the launch of the space telescope James Webb in 2018, which will scan the atmospheres of planets near other stars.
What NASA wants to avoid at any cost, so it is a repetition of the experience of missions "Vikings" back in the 1970-ies, when the analysis of the chemistry of Martian soil at first gave proof of life in it, and then was counted a false positive. The authors of the experiment that the life of the Vikings still found.
"I remember the consequences of this", says James Kasting, Professor of Geosciences at the University of Pennsylvania. "NASA was criticized for the search for life on the planet, which first had to explore, and for not thoroughly thought experiment. They hope to avoid repeating it."
But getting this definition does not mean come to a consensus on what to look for. "We are hot debates on this subject," says Kasting. "Therefore, going, actually".
In our own solar system, scientists are wondering what kind of existing or extinct life we might find on Mars, the icy satellites of Europe and Enceladus, or in a strange methane lakes of Titan. If scientists find DNA or RNA, obviously, it will be a direct pointer to the existence of something alive, unless, of course, exclude the possibility of contamination.
But alien life is unlikely to have the same type of genetic material. In fact, its chemistry can be completely unrecognizable. "If I just start to perform a normal search procedure of the life we know on Earth, there is no reason to believe that it will help in the definition of life from a slightly different biochemistry," says Steve Benner of the Foundation for applied molecular evolution. "It would be quite strange to look for long, extended molecules, separated by regularly recurring sections".
The Search for life outside our Solar system presents other problems, since it is impossible to carry out interstellar travel, which would allow spacecraft to visit the planet from other stars and examine the dirt on its surface. All that scientists can do is look through a telescope and sift the world in search of clues".
With these restrictions, says Benner, perhaps the best we can do is to look for such life on earth. However, not all scientists agree with him. A clear signal from a distant planet in another system would be the presence of large amounts of oxygen and gases like methane or nitrous oxide.
"And oxygen, and methane and nitrous oxide are produced mainly by biology, so it is very difficult to create high concentrations of these gases, especially two or three at a time, in the absence of life," says Casting.
"As a field geologist, I strongly believed that you need to send people like me on the surface of Mars, open a bunch of rocks and search for signatures of Martian life first," says Ellen Stofan, recently retired from NASA. "Because it's not enough just to say: here we have one molecule that has a biological origin. You need a lot of molecules, a lot of samples to understand the state of life beyond Earth. The idea that in the next 20 years we will finally begin to answer these questions, literally circling the head."
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