Why is liquid water on Mars necessary for life?
Yesterday, NASA revealed the 鈥渟trongest evidence yet that intermittently on present-day Mars.鈥� NASA's Mars Reconnaissance Orbiter (MRO) detected hydrated salts in the recurring slope lineae (RSL), the streaks that appear on the Red Planet鈥檚 slopes.
"We can look and see if we can determine if there is some sort of that may be supplying these [RSL features]. We don't know that 鈥� there are other theories, other ideas 鈥� but that is actually the next step," Jim Green, director of NASA's Planetary Science division, said during the press briefing. "So if there is indeed those kind of resources that we can begin to probe, we might be able to answer that question pretty quickly."
Does the discovery of liquid water mean there is life on Mars? Not so fast.
"Finding evidence for flowing water is ," says National Geographic's Nadia Drake. "Right now, scientists don鈥檛 know where this water is coming from, or if the chemistry in these Martian seeps is even life-friendly."
Planetary scientists have long said that where water exists, life may also exist. 鈥淲ater is to moving life beyond its basic building blocks; thus, searches for extraterrestrial life usually involve a search for liquid water,鈥� writes NASA.
But what makes water the necessary liquid for sustaining life?
鈥淧art of the reason is that we've never discovered an organism that's proven otherwise,鈥� says Jonathan Attebery, science writer for 鈥�.鈥� Water facilitated the beginning of life on Earth, 鈥渁cting as a medium in which organic compounds could mix with one another.鈥�
As a solvent, water allows vital chemical reactions to occur. 鈥淔rom the list of potentially abundant solvents in the universe, to support a complex ecosystem,鈥� says Steve Nerlich of Universe Today in an article for io9.
Furthermore, liquid water 鈥� like metabolites and nutrients from one place to another鈥� and is also capable of 鈥渂ending enzymes,鈥� the proteins that catalyze chemical reactions, says Peter Tyson, editor in chief of NOVA Online.
"Given that life on Earth is so dependent on water, and given that water is so prevalent in the universe, we don't feel that we're going out on a limb to say that ," said Neil deGrasse Tyson, an astrophysicist and director of the Hayden Planetarium at the American Museum of Natural History, in an interview with PBS.
It isn鈥檛 impossible that lifeforms exist that don鈥檛 require water to survive, but they would not resemble life on Earth. Biochemistries based on other solvents 鈥渟eem likely to be where the rate of development of biological diversity and evolution may be very slow,鈥� says Mr. Nerlich.
According to Mr. Attebery, 鈥渨e simply to say whether or not life could exist without water. We know with certainty, however, that life on Earth definitely couldn't.鈥�
