Is life on Earth unique in the universe? That is arguably the most exciting unsolved question in all of science, but the vastness of space and the technical limitations of interstellar travel significantly limit our ability to answer it. Fortunately, the answer may lie closer to Earth.
Scientists hunt for signs of extraterrestrial life in many ways. But only by directly observing “biosignatures” (physical traces of life or life-induced processes) can its existence be confirmed. That requires landing instruments on planets and moons, and for now is only feasible in our Solar System. Where life once existed, evidence could be preserved in rocks or soil, or where it persists, in the form of microbes or more complex entities.
The latest attempt to detect these started in February, when NASA’s “Perseverance” rover survived the perilous journey to Mars’s surface, with the goal of determining if life ever emerged on The Red Planet.
Mars is special for two reasons: it is the closest planet to Earth we can land and control robotics on for sustained periods of time, and once had the conditions (likely) necessary for the emergence of life. Although the planet is now mostly a dry, dusty, freezing desert, this wasn’t the case four billion years ago, when Mars had rivers and lakes of water, and an atmosphere almost as thick as the Earth’s today. Mars is both a promising location where life may have emerged, and somewhere humanity can readily land robotics.
There is however no guarantee that life ever formed on Mars. Attempting to answer this is the primary aim of NASA’s “Mars Exploration Programme”: a series of missions to study the planet in detail with orbital spacecraft and surface landing instruments, of which Perseverance is the sixth installment.
Perseverance is a six-wheeled robotic buggy packed full of science instruments. It can measure the weather on Mars and investigate its surroundings above and below the ground. Over the next few years, Perseverance will travel the Martian landscape, photographing it in high resolution, and analysing rocks and soil to measure for the presence of biosignatures and other molecules.
It was landed in Mars’ “Jezero Crater”: the dried out landscape where a river once met a great lake. If life began on Mars in a similar location to where it is believed to have formed on Earth, Jezero is amongst the best places that its biosignatures could be found.
In 2012 NASA landed the “Curiosity” rover on Mars, which is still in operation. Perseverance hosts a number of new and improved instruments in comparison to Curiosity, but there are two other significant differences between their missions. Whilst Curiosity only analysed Martian rocks and soils, Perseverance will analyse and store samples awaiting a future mission to return these to Earth (2031 at the earliest). Since powerful laboratory analysis (only possible on Earth) may be essential to assess Martian rocks and soil for signs of life, retrieving these samples may prove vital.
Secondly, Perseverance is equipped with a drone, and will make the first attempt to fly a small helicopter on another planet. Despite being limited to 5m altitudes and 90 second flight times, this could prove to be important technology for future surveys and human-missions to Mars.
If Perseverance doesn’t detect or collect any biosignatures, that could mean one of two things: life never formed on Mars (if not, why?), or it did and Perseverance missed it (if so, how and where should we try looking again?). Minimally, this mission will improve human understanding of Mars’ environment, atmosphere, and surface and underground geology, important for preparing future scientific and exploratory missions.
Alternatively, Perseverance may finally provide proof that life emerged elsewhere in the Universe. This answer isn’t likely to arrive for some time, but whether that is measured in years, decades or centuries, humanity must continue working towards this discovery, whether it is made by Perseverance on Mars, or elsewhere.
• More info on Perseverance here