Will Drilling Find Extant Life on Mars?
By: Nicole Willett
If life exists on Mars today, it almost certainly resides beneath the surface. The harsh conditions on the Martian surface — intense ultraviolet radiation, extreme cold, and very low atmospheric pressure — make the surface inhospitable to life as we know it. But just a few meters below, conditions may be dramatically different. Subsurface drilling on Mars could be the key to one of the most profound discoveries in human history.
Why Look Underground?
The Martian subsurface offers several advantages for life:
Protection from radiation: The surface of Mars is bombarded by ultraviolet radiation and cosmic rays. Just a meter or two of regolith provides significant shielding from these harmful radiation sources.
Stable temperatures: While surface temperatures on Mars can swing by over 100 degrees C in a single day, subsurface temperatures are much more stable, remaining relatively constant year-round.
Liquid water: At sufficient depth, the combination of pressure from overlying material and geothermal heat could maintain liquid water. On Earth, we find microbial life in deep aquifers and rock formations kilometers below the surface. Similar environments may exist on Mars.
Chemical energy: Subsurface rock-water interactions can produce chemical energy that microorganisms can use for metabolism, independent of sunlight. This process, known as chemolithotrophy, supports vast ecosystems deep within Earth’s crust.
Analogs on Earth
Studies of Earth’s deep biosphere provide strong support for the possibility of subsurface life on Mars. Microorganisms have been found in some of the most extreme subsurface environments on Earth:
- Deep gold mines in South Africa, where bacteria live kilometers below the surface, deriving energy from the radioactive decay of uranium in surrounding rocks.
- Basalt aquifers in the Columbia River region, where microbial communities thrive in the spaces between rocks, metabolizing hydrogen produced by water-rock interactions.
- Under the Antarctic ice sheet, where microbial life persists in subglacial lakes isolated from the surface for millions of years.
If life can thrive in these environments on Earth, similar organisms could potentially survive in comparable environments on Mars.
The Challenge of Drilling on Mars
Drilling on Mars presents formidable technical challenges:
- Mass and power constraints: Drilling equipment is heavy and requires significant power. Both are limited commodities on Mars missions.
- Autonomous operation: Current Mars missions operate with significant communication delays, meaning drilling equipment must be capable of autonomous or semi-autonomous operation.
- Sample handling: Retrieving a subsurface sample while maintaining its integrity and preventing contamination from surface materials or terrestrial microbes is extremely challenging.
- Depth requirements: Reaching liquid water may require drilling tens to hundreds of meters, far beyond the capabilities of current Mars rovers. Curiosity’s drill can penetrate only a few centimeters into rock.
Current and Planned Missions
The ExoMars Rosalind Franklin rover, developed by the European Space Agency, was designed to drill up to 2 meters into the Martian surface — deeper than any previous mission. At this depth, samples would be partially shielded from surface radiation, increasing the chances of finding preserved organic molecules or even viable microorganisms.
Future missions may carry even more capable drilling systems. Concepts for deep drilling on Mars include rotary-percussive drills, melt probes for penetrating ice deposits, and wireline drilling systems adapted from terrestrial oil exploration.
The Implications
The discovery of extant life on Mars would be one of the most significant scientific findings in history. It would demonstrate that life is not unique to Earth and that the conditions for life are more common in the universe than previously thought. It would also raise profound questions about the relationship between Earth life and Martian life — whether they share a common origin, or whether life arose independently on two neighboring planets.
Even a negative result from deep drilling would be scientifically valuable, placing important constraints on the conditions under which life can arise and persist.
The question of whether drilling will find extant life on Mars remains open, but the scientific rationale for looking is compelling. The subsurface of Mars may hold the answer to one of humanity’s oldest questions: are we alone?