A team of scientists has just discovered the longest organic molecules ever seen on Mars, the fourth planet from the Sun and an attractive destination for humanity’s search for life beyond Earth.
Today, Mars is inhospitable, with significant temperature fluctuations, a thin atmosphere, and an apparent lack of liquid water on the planet’s surface. But according to a new study published today in the Proceedings of the National Academy of Sciences, large molecules found on Mars are apparently as old as life on Earth, raising questions about biological activity on ancient Mars.
The molecules are long carbon chains containing up to 12 consecutive carbon atoms. The molecules have been on Mars for about 3.7 billion years, undisturbed by geologic activity, moisture, or heat. The molecules date back to about the same time as the earliest known signs of life on our planet.
“Curiosity has been traveling around Mars for many years now, discovering new details about the planet’s ancient environment. A key element of this environment is carbon, an element that is vital for life and useful for binding molecules, including DNA and RNA. According to the French National Center for Scientific Research (CNRS), carbon chains “may have features similar to fatty acids produced on Earth as a result of biological activity.”
The discovery of these organic molecules provides important insight into potential biological processes on early Mars, but to be clear, it is not proof of past or present life. It does, however, suggest that the building blocks necessary for life as we know it were present – and that Mars may have once had the right conditions to support it.
“Although the source of these organic molecules on Mars could not be determined in this study, these organic substances could have been formed by geological processes on Mars (non-biological chemical reactions such as hydrothermal activity), they were delivered to the surface of Mars by meteorites, or they are organic remnants of ancient Martian biology,” said Daniel Glavin, senior sample return scientist at NASA’s Goddard Space Flight Center. Goddard Space Flight Center at NASA and co-author of the paper, in an email to Gizmodo.
The team, which included scientists from the CNRS and several other institutions, made their findings using the Sample Analysis at Mars (SAM) laboratory aboard Curiosity. SAM contains a gas chromatograph and a mass spectrometer that can identify individual molecules in samples collected by the rover. Curiosity has already seen organic matter in Martian clay rocks, but the new study describes the longest chains ever detected. The discovery of long carbon chains on Mars is significant because it shows that NASA scientists are on the right track to finding signs of life – or at least what underlies life on Earth.
Curiosity is still working, but successors to its mission to explore Mars’ ancient past are on the way. The ESA ExoMars mission, scheduled to launch in 2028, and the joint NASA/ESA Mars Sample Return mission will help scientists better assess the composition of Mars in the ancient past – and, indirectly, the potential for ancient life on its surface.
“The discovery of long-chain hydrocarbons that have been preserved (rather than completely destroyed by ionizing radiation) in ancient sedimentary rocks on Mars reinforces the current strategy of searching for ancient signs of life in the near-surface layers of Mars that may have similar characteristics to life on Earth,” added Mr. Glavin. “We know from the analysis of meteorites and samples returned from the asteroids Bennu and Ryugu by the OSIRIS-REx and Hayabusa2 missions that the chemical constituents of life, which include amino acids (used to make proteins), carboxylic acids (used in cell membranes) and nucleotides (components of DNA and RNA), were widely distributed throughout the solar system, and these chemical constituents should have been delivered to Mars.”
“But the million-dollar question: Did the organic chemistry necessary for the formation of life exist on Mars, to move from these basic chemical building blocks to larger and more complex structures such as the proteins and nucleic acids found in cells?” added Glavin.
Liquid water once existed in huge reservoirs and lakes on Mars. Now that the water has long since dried up, the space agency’s rovers are set to explore these once-wet environs in search of signs of primitive life similar to that which barely survives in Earth’s wetter climate. Scientists have seen signs of liquid water beneath the Martian surface, although such speculative findings need to be more carefully studied before scientists can say for sure.
In 2023, the Perseverance rover found preserved organic molecules on Mars – by no means proof that life once existed on the Red Planet, but an encouraging indicator that the conditions for life as we know it once existed.
New techniques could make it easier to detect signs of life on Mars and possibly explain how life that may have once existed there disappeared when the Red Planet became barren and inhospitable.
In addition to Mars, the CNRS release says that the same international teams will create a SAM-like instrument for Dragonfly, a quadcopter that will explore Saturn’s moon Titan starting in the mid-2030s.
