In 1964, biologist George G. Simpson criticized exobiology, the study of life outside of Earth, as a science without a subject. Even after exobiology was reincarnated by NASA at the turn of the millennium as astrobiology, Simpson’s accusation still holds some truth: to date there is no direct, unambiguous evidence for extraterrestrial life. Yet the NASA Astrobiology Institute holds yearly seminars and the Journal of Astrobiology has been publishing papers on the subject for a decade. NASA’s Curiosity rover is currently on a mission which includes searching for Martian life. In a paper published this August in Nature and provocatively titled “Astrobiology: Frontier or Fiction,” a physicist and a biologist lay down a hard critique of the state of Astrobiology in 2012.

While Astrobiologists may not have any aliens to dissect, they make due with theory and correlation. The authors of the paper say it is akin to the study of theoretical particles. One example is the study of extremophiles, microorganisms that live in extreme environments like boiling hot geysers, brine pools at the bottom of the ocean, or highly toxic lakes. The reasoning goes that if life on Earth can thrive in such extreme conditions, it may be able to survive in the harsh environments of alien worlds.

Astrobiologists also look at various heavenly bodies and compare the conditions there to life-sustaining environments on Earth. The article cites the evidence for water in the Martian past and the liquid water oceans on moons like Jupiter’s Ganymede and Europa and Saturn’s Titan and Enceladus.

The authors do write that astrobiology is a worthy pursuit of science. As they say, it would have been foolish for chemists to stop with the first periodic table when the gaps in the elements clearly showed where undiscovered ones might exist. In the same way, the tree of life here on Earth allows us to imagine that other and different kinds of trees might exist.

However, they write, the danger lies in researchers using “astrobiology” as a buzzword to reel in grant money. An example is the so-called “arsenic-based DNA” of a microbe discovered in a saline Californian lake that captured the attention of science news earlier this year. Some astrobiologists jumped on this as evidence of a “shadow biome,” or groups of alternate life forms living side-by-side our own. However, subsequent analysis found nothing special about the DNA of these microbes.

The authors say biology is the last branch of science yet to prove its worth outside of Earth. Yet they believe that if NASA and other space agencies obtain funding on a scale with the construction of the Large Hadron Collider, we will be able to answer the question of whether extraterrestrial life exists in our solar system within a couple of decades. The most likely target for such a mission is the aqueous ocean beneath the icy surface of Europa, which is kept warm and liquid by the gravitational forces of Jupiter.

Sources:

Lazcano, Antonio; Hand, Kevin p. “Astrobiology: Frontier or Fiction.” Nature. 2012, Vol. 488(7419), pp. 160-1

Image credit NASA

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