Arsenic and old lakes…

Earlier this week, NASA announced that it had it was going to hold a big press conference on Thursday to make a major announcement. For most of the week, the blogosphere was crazy with speculation. Had NASA found extraterrestrial life? Did they find an Earth-like exoplanet? Were they finally going to reveal secret mission of the X-37B space plane? Nope. NASA threw the proverbial screwball on Thursday that it had in fact discovered alien life…in California.

Before any Area 51/Roswell/government conspiracists start screaming “I told you so!”, NASA found “alien”, not “extraterrestrial” life. The 760,000 year-old Mono Lake is located just east of Yosemite National Park in the Sierra Nevada mountains. It has been cut off from its freshwater sources for over 50 years, so it’s chemical composition of the water has increased drastically in salinity (saltiness), alkalinity, and now has a large percentage of arsenic. Arsenic is notoriously poisonous to humans and other multicellular life because of its chemical similarities to phosphorus, one of the main building blocks of life. Phosphorus is elemental in the development of the energy-carrying molecule found in all cells (adenosine triphosphate or ATP) and the phospholipids that make up all cell walls; phosphorus (along with carbon, hydrogen, nitrogen, oxygen, and sulfur) is considered to be one of the six basic building blocks of all known life. Notice the lack of arsenic in that list.

A NASA-funded research project that was researching the ecology of Mono Lake found a new strain of the common bacteria group of Gammaproteobacteria that successfully substituted arsenic for phosphorus in all of its cellular structures. The new strain, GFAJ-1, is the FIRST and ONLY living organism ever found to incorporate arsenic in its cellular makeup; it’s also the only organism ever discovered to not have phosphorus in its cellular makeup. The new microorganism’s DNA has been characterized as “unlike anything ever seen before on Earth”.

Life just never ceases to amaze us. No matter where we look for life, no matter how harsh or improbable the environment is, we seem to find life there: rocks miles underground, the very depths of the ocean, areas deprived of oxygen, areas of extreme heat and cold. The extremely resilient, unique organisms that can survive these odd environments are known as extremophiles. I’ve said it before: no matter what, life finds a way. The discovery is huge (and bankrolled by NASA) because it has major implications as we continue to search for extraterrestrial life. It was believed that any life that we found beyond Earth would be similar to that found on Earth (and therefore probably found in similar environments), but this new expansion of the definition of life on Earth opens the door to new possibilities. Some scientists have speculated that there may be non-carbon-based lifeforms on other worlds (all life on Earth is carbon-based) or that life exists that could be methane- or ammonia-soluble (life on Earth is water-soluble). We know that Titan, the largest moon of Saturn, has large liquid methane seas and oceans covering its surface, so if methane-soluble life does exist, Titan would be a great place to look.


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