Curiosity Rover Finds Organics on Mars may be Product of Life

James Maynard
Mar 5 · 4 min read

The Curiosity Rover found organic materials on the Martian surface may be the product of ancient life on Mars.

The Curiosity rover has found evidence of thiophenes, a type of organic material, on Mars in 2018. A new study now suggests these thiophenes may be the product of ancient bacteria which developed on Mars in the distant past.

Thiophenes are naturally found on Earth in crude oil, coal and (strangely enough) white truffles. This organic material, usually seen as a clear liquid with a mildly unpleasant smell, is widely used in the production of pharmaceuticals, dyes, and agrochemicals.

The Curiosity rover recently returned its most-detailed panorama ever of the Martian landscape (click here for full photo). Image credit: NASA/JPL-Caltech/MSSS

“We identified several biological pathways for thiophenes that seem more likely than chemical ones, but we still need proof. If you find thiophenes on Earth, then you would think they are biological, but on Mars, of course, the bar to prove that has to be quite a bit higher,” Washington State University astrobiologist Dirk Schulze‑Makuch explains.

I Just Felt a Real Chemistry

Thiophene molecules are composed of four atoms of carbon and an atom of sulfur, bonded together as a ring. Both of these chemicals are essential to life on Earth.

A model of one of four forms of thiophene. Image credit: Ben Mills

“[T]he recent discovery of various classes of organic matter in martian sediments by the Curiosity rover seems to strongly suggest that indigenous organic compounds exist on Mars. One intriguing group of detected organic compounds were thiophenes, which typically occur on Earth in kerogen, coal, and crude oil as well as in stromatolites and microfossils,” researchers wrote in an article detailing their study, published in the journal Astrobiology.

However, non-biological reactions may be responsible for the presence of these molecules on the Martian surface. One possibility is that thiophenes arrived on Mars, trapped inside meteors. They could have also been produced through thermochemical sulfate reduction, which involves heating a number of compounds to 120 Celsius (248 Fahrenheit).

Bacteria could have also initiated a sulfate reduction process billions of years ago, when Mars was far wetter — and warmer — than it is today. This process would have resulted in the production of thiophenes seen by Curiosity. There also exists a possibility that ancient Martian bacteria consumed thiophenes as part of their life cycle.

“Curiouser and Curiouser,” Cried Alice

The Curiosity rover, which landed on Mars in August 2012, utilizes techniques which break molecules apart during analysis. Because of this, researchers are only able to examine fragments of the samples being studied.

A look at how the Curiosity rover was utilized to take the new 1.8 billion-pixel panorama of the Martian surface. Video credit: NASA/JPL

The Rosalind Franklin rover, expected to launch in July 2020, is equipped with the Mars Organic Molecule Analyzer (MOMA). The instrument is less destructive to samples than the technology aboard Curiosity, allowing it to study larger molecules.

“Mars ain’t the kind of place to raise your kids
In fact, it’s cold as hell
And there’s no one there to raise them if you did.” — Rocketman, Elton John

Like its namesake, the Rosalind Franklin rover, one of a number of spacecraft headed to Mars in 2020, will be a pioneer in understanding the chemical makeup of life.

The Rosalind Franklin rover, part of the ExoMars mission, will provide a robotic laboratory on Mars, searching for signs of life, past or present. Video credit: ESA

This upcoming Mars rover will have the ability to measure the relative concentrations of different isotopes of carbon and sulfur in Martian samples.

Isotopes are variations of atoms having various numbers of neutrons — for instance, hydrogen normally has one proton and no neutrons, but it can also come as deuterium with a proton and neutron, or tritium which has a proton and two neutrons.

Biological processes tend to use the less-massive isotopes of atoms, since these isotopes require lower amounts of energy to trigger reactions. This results in the by-products of life exhibiting different isotope ratios than the same chemicals produced by non-biological reactions. This difference can be a telltale sign of life.

“As Carl Sagan said, ‘extraordinary claims require extraordinary evidence.’ I think the proof will really require that we actually send people there, and an astronaut looks through a microscope and sees a moving microbe,” Schulze‑Makuch said.

James Maynard is the founder and publisher of The Cosmic Companion. He is a New England native turned desert rat in Tucson, where he lives with his lovely wife, Nicole, and Max the Cat.

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The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time

James Maynard

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The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time

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