Is There Oil on Mars?
Most geologists believe that oil originated on Earth mostly from the remains of ancient marine microorganisms — primarily plankton, algae, and bacteria — that accumulated on seafloors, were buried under layers of sediment, and transformed under extreme heat and pressure into oil and gas.
Most of the organic raw materials are traced to the Mesozoic era, 66 to 252 million years ago, but some deposits are much older, originating from algae and bacteria in ancient seas.
Life started on Earth about 4.2 billion years ago in the form of the Last Universal Common Ancestor (LUCA), which was DNA-dated recently here. However, most rocks of that age have been heated so many times that any fossils they may have contained are gone. In 1998, a team led by geologist Birger Rasmussen of the University of Western Australia discovered microscopic drops of fluid oil preserved within mineral grains in rocks more than 3 billion years old in Australia’s Pilbara region. In 2005, Rasmussen reported here evidence that ancient oil in 3.2-billion-year-old rocks in Western Australia was produced from decayed organic matter. He studied two well-preserved sequences of black shale, which are 2.63 and 3.2 billion years old, and discovered thin, discontinuous streaks of cellular material — kerogen, a waxy precursor to fossil fuels formed from organic matter and commonly found in much younger shales that are known oil producers. Both shales also contained microscopic nodules of bitumen, a tar-like remnant left behind when oil migrates out of the shale. Rasmussen concluded that the abundance and extent of the kerogen in the shales indicates that an ancient ocean was already teeming with enough single-celled life 3.25 billion years ago to support widespread oil generation.
The history of Earth is marked by various periods. Precambrian spans the period from Earth’s formation, 4.6 billion years ago, to the Cambrian Period’s start, about 0.5388 billion years ago. Within that time frame, the Archean Period, lasting from about 4 billion to 2.5 billion years ago, was the critical era when Earth’s crust solidified, oceans formed, and life appeared. The first, simple unicellular organisms, such as cyanobacteria, thrived during this time, producing the oldest fossils known as stromatolites. In 2021, Rasmussen and colleagues reported here the discovery of ancient oil in 1.88-billion-year-old Gunflint stromatolites and microfossils. The thermally altered oil was found to fill pores and fractures and coat grain surfaces, originating from algae and bacteria in ancient Precambrian seas.
The presence of oil-bearing fluid inclusions and pyrobitumen in Archean rocks suggests that a large biomass existed on Earth as early as 3.25 billion years ago. Indeed, abundant microbial activity was preserved in 3.4 billion years old colloform pyrite grains from Archean sedimentary environments , as reported in a paper published this month (April 2026) here.
But what happened at the same time on Earth’s twin, Mars?
As early as 3.25–3.4 billion years ago, Mars was a wet planet. As discussed here, here and here, surface geological features suggest that liquid water existed in Martian rivers, lakes, oceans and aquifers, more than 3 billion years ago. Indeed, the existence of large volumes of liquid water on the surface of Mars was also supported here by seismic and gravity data down to 20 kilometer depths near NASA’s InSight lander. Mars lost the persistent bodies of liquid water on its surface after most of its atmosphere escaped, as discussed here. Subsequently, the ancient surface water had been incorporated in Martian minerals, buried as ice, sequestered as liquid in deep aquifers, or lost to space.
Life could have started on Mars earlier than on Earth. This is because the heat trapped during planet formation scales as the planet’s volume but escapes through its surface. The surface to volume ratio of Mars is 1.87 times larger than that of Earth, implying that it cooled to temperatures capable of supporting the chemistry of life before Earth.
If plankton, algae, and bacteria lived in Martian rivers, lakes, oceans, and aquifers, their dead relics could have been subjected to similar processes that produced ancient oil in the 3.25-billion-year Archean rocks studied by Rasmussen.
In case Martian oil exists, it could fuel a future Martian economy. The oxygen needed for combustion or breathing can be made out of electrolysis of water, using sunlight. Finding oil could be of great value to space entrepreneurs like Elon Musk. Underground petroleum deposits could be searched on Mars through the same techniques adopted on Earth, including localization through seismic or gravity surveys, followed by drilling deep boreholes. NASA’s InSight lander recorded over 1,300 marsquakes, as discussed here.
Most importantly, the discovery of ancient Martian oil would be of great value also to science, as this oil would provide a record for how early life may have started on Mars and whether it resembled life on Earth. In case the chemistry of early Martian life was the same as life-as-we-know-it in the ancient Precambrian oceans on Earth, this discovery would suggest that perhaps the two planets have a common ancestry.
During the Late Heavy Bombardment period, 4.1 to 3.8 billion years ago, a surge of asteroids and comets cratered the Earth and Mars, potentially exchanging microbial life inside the rocks that were transferred between the two planets. Since Mars cooled first to habitable temperatures, this process of panspermia was more likely to deliver Martian life to Earth before it went the other way around. An early `French kiss’ between Earth and Mars could have resulted in identical early microbes on both.
With this perspective, we might all be Martians and Musk’s desire to establish a human base on Mars resembles the desire of some adults to return to their childhood home. The first astronauts in the Solar System may have been tiny microbes, predating human astronauts by billions of years.
Finding Martian oil as a trace of the chemistry of life-as-we-know-it holds the potential of unraveling our cosmic roots. Let the search begin.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, former director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics (2005–2026), and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
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