NASA’s flagship Mars rover, Curiosity, has been combing the surface of Mars for signs of life for almost six years. These hints of habitability, called biosignatures, can come in many forms—from unique sediment deposits to the abundance of certain gases in the thin Martian atmosphere.
One possible biosignature on Mars—or a sign leading to potential biosigantures—is the presence of organic compounds. Almost all molecules containing carbon are organic compounds, and these molecular structures are frequently produced and consumed by living organisms. There are other ways to produce organic compounds, so they are not a smoking gun for life—but they are an awfully good sign.
And Curiosity just found an abundance of organic compounds on Mars.
Two studies (1, 2) published today in the journal Science solve past mysteries surrounding organic compounds on Mars. The first study found several new organic compounds in samples of ancient Martian mudstone that is roughly three billion years old, while the second charted seasonal fluctuations of one of the most basic organic compounds: methane.
The mudstone samples analyzed by Curiosity came from Confidence Hill and Mojave, two sites near the base of Mount Sharp in Gale crater. Curiosity drilled samples of mudstone in a region that is thought to have been a lake about three and a half billion years ago. The rover heated the Martian soil to above 500 degrees Celsius and analyzed the compounds released in the gases with its Sample Analysis at Mars (SAM) instrument. Numerous organic compounds were discovered, including thiophene, 2- and 3-methylthiophenes, methanethiol, and dimethylsulfide.
The researchers, led by NASA biogeochemist and geologist Jennifer Eigenbrode, note that because the organic molecules differ by just one carbon sidechain, they may be fragments of larger and more complex molecules. Eigenbrode says that fact strengthens the evidence that the region in Gale crater could have been habitable in the distant past.
Now, samples taken from two different drill sites on an ancient lakebed have yielded complex organic molecules that look strikingly similar to the goopy fossilized building blocks of oil and gas on Earth.
The rover also discovered traces of methane in the Martian atmosphere, which was reported in a second paper in Science.
“The detection of organic molecules and methane on Mars has far-ranging implications in light of potential past life on Mars,” said Inge Loes ten Kate, a Utrecht University scientist in an accompanying article in Science. “Curiosity has shown that Gale Crater was habitable around 3.5 billion years ago, with conditions comparable to those on the early Earth, where life evolved around that time.
“The question of whether life might have originated or existed on Mars is a lot more opportune now that we know that organic molecules were present on its surface at that time,” Kate said.
NASA’s Thomas Zurbuchen said that “with these new findings, Mars is telling us to stay the course and keep searching for evidence of life. I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet.”
Mr Americana, Overpasses News Desk
June 7th, 2018