A team of scientists just discovered the longest organic molecules yet seen on Mars, the fourth planet from the Sun and and a tantalizing venue for humankind’s search for life beyond Earth.
Mars today is inhospitable, with significant temperature fluctuations, a thin atmosphere, and an apparent dearth of liquid water on the planet’s surface. But according to new research, published today in Proceedings of the National Academy of Sciences, large molecules found on Mars apparently are as old as life on Earth, raising questions about biological activity on an ancient Mars.
The molecules are long carbon chains, containing up to 12 consecutive carbon atoms. The molecules sat preserved on Mars for about 3.7 billion years, undisturbed by geological activity, moisture, or heat. The molecules date to about the same time as the earliest-known signs of life on our planet.
Curiosity has roved Mars for years, revealing new details of the planet’s ancient environment. Key to that environment is carbon, an element that is both vital to life and useful for bonding molecules, including DNA and RNA. According to a French National Centre for Scientific Research (CNRS) release, the carbon chains “could exhibit features similar to the fatty acids produced on Earth by biological activity.”
The discovery of these organic molecules offers crucial insights into potential biological processes on early Mars, but to be clear, it’s not evidence of past or present life. What it does tell us, however, is that the building blocks necessary for life as we know it were present—and that Mars may once have had the right conditions to support it.
“Although the source of these organic molecules on Mars could not be established in this study, these organics could have either been formed by geological processes on Mars (non-biological chemical reactions such as from hydrothermal activity), they were delivered to the surface of Mars from meteorites, or they are the organic remnants of an ancient martian biology,” said Daniel Glavin, a senior scientist for sample return at NASA’s Goddard Space Flight Center and co-author of the paper, in an email to Gizmodo.
The team, which included scientists with CNRS and several other institutions, made its findings using the Sample Analysis at Mars (SAM) laboratory aboard Curiosity. SAM contains a gas chromatograph and mass spectrometer, which make it possible to identify isolated molecules in samples collected by the rover. Curiosity has seen organic matter in Martian mudstones before, but the new research describes the longest chains yet identified. Finding long carbon chains on Mars is significant because it shows that NASA scientists are on the right track in the way that they search for signs of life—or at least, the things that undergird life on Earth.
Curiosity is still going strong, but successors in its mission of understanding Mars’ ancient past are already on the way. ESA’s ExoMars mission, set to launch in 2028, and the joint NASA-ESA Mars Sample Return mission will help scientists better assess Mars’ composition in the ancient past—and by proxy, the potential of ancient life on its surface.
“The discovery of long-chain hydrocarbons that were preserved (and not completely destroyed by exposure to ionizing radiation) in ancient sedimentary rocks on Mars, bolsters the current strategy of searching for ancient signs of life in the martian near-surface that may share similar characteristics with life on Earth,” Glavin added. “From the analysis of meteorites and samples returned from asteroids Bennu and Ryugu by the OSIRIS-REx and Hayabusa2 missions, we know that the chemical building blocks of life that include amino acids (used to form proteins), carboxylic acids (used in cell membranes) and nucleobases (components of DNA and RNA) were widespread throughout the solar system and these chemical building blocks would have been delivered to Mars.”
“But the million-dollar question is: Did the life forming organic chemistry required to go from these basic chemical building blocks to larger and more complex structures like proteins and nucleic acids found in cells ever occur on Mars?,” Glavin added.
Liquid water once existed in vast reservoirs and lakes on Mars. Now long dried up, space agency rovers are tasked with exploring those once-wet environs, seeking signs of primordial life similar to those which eke out existence in Earth’s wetter climes. Scientists have seen signs of liquid water beneath the Martian surface, though such speculative findings will require more scrutiny before scientists can say for sure.
-
A SAM replica at NASA Goddard. Photo: Caroline Freissinet
In 2023, the Perseverance rover found preserved organic molecules on Mars—by no means a confirmation that life once existed on the Red Planet, but an encouraging indicator that the conditions for life as we know it once did.
New methods could make it easier to spot signs of life on Mars, and perhaps explain how the life that may have once existed there lost out as the Red Planet became barren and inhospitable.
Beyond Mars, the CNRS release stated that the same international teams will build an instrument like SAM for Dragonfly, a quadcopter that will explore Saturn’s satellite Titan beginning in the mid-2030s.
