The Question of Life on Mars

The answer to whether there was ever life on Mars will be answered when the Nasa Perseverance rover samples return in 2033. But why should we care?

Are we alone? It’s a question asked from the beginning of humanity. As curious beings, we want to know how life develops, where life comes from.

It’s hard to answer these questions because we only have one example of life, here on Earth. But we can use Mars to test hypotheses to answer questions about ourselves. This is the opinion of Nina Lanza, team lead for space and planetary exploration in space and remote sensing (ISR- 2) at Los Alamos National Laboratory. She is on the science teams for the ChemCam instrument on board the Nasa Curiosity rover and the SuperCam instrument on the Perseverance rover.

“These ancient rocks we have provide a window into habitable environments from the distant past, that can help us understand what those environments might have looked like on Earth. So, we can understand a lot about our own origins by going to another planet,” says Lanza. It will also revolutionise our understanding of our solar system and prepare for human explorers to the Red Planet, she adds. Lanza is talking at The Explorers Club annual meeting held this year at Monaco Yacht Club.

Right now, there are two Nasa-led rovers exploring the Martian surface, Curiosity and Perseverance. While Perseverance is a relative newcomer to the planet that arrived in 2020, Curiosity has been in situ for the past 10 Earth years.

Each rover is equipped with an instrument payload designed to answer fundamental questions about Martian geology, climate, habitability, and the possibility for past life. “While Mars and Earth have had very different histories and evolutionary paths, our deep and evolving knowledge of Earth provides us with critical context in which to interpret data returned from Mars,” says Lanza.

“Mars today is much less habitable than it was in the past. To look for evidence of life, you must look for where the present-day oases, where would life be today, areas more hospitable than average like caves, ice and salts,” she adds.

Currently the Perseverance and Curiosity rovers are in the Gail and Jezero crater lakes. Scientists are looking for biosignatures, chemistry, isotopes, different minerals and structures, to build up a picture of evidence of life and assessing geology and climate.

Does she believe that the rovers will return with evidence of life on Mars? “I think it’s plausible enough that I’ve dedicated a large portion of my professional career looking for it,” she laughs. “It is not a crazy thought. Yes, we’ve not yet seen proof, but I don’t think we’ve sent the right tools to do so. That’s why these samples are so important for us and future generations to work on,” adds Lanza. 

“If we find any evidence of ancient life on Mars that tells us something fundamental about life, that it is probably everywhere. The chemistry that makes up life here on Earth is everywhere in the universe as far as we can tell, it is very common.”

She adds: “But if there wasn’t life on Mars, if it didn’t happen, that tells us something exciting too. It would be shocking, in many ways, all the chemistry was there, so what happened to make Earth different?”

The year 2033 is a long time to wait for the answer, but the journey back from Mars takes a while. The Earth return orbiter and sample retrieval lander will arrive in 2027 and 2028, respectively, the samples are expected to arrive on Earth in 2033. The Mars sample return will be Nasa’s and the European Space Agency’s most ambitious multi-mission campaign in history, bringing back samples from the Red Planet for the first time.

Will the mission help to prove whether humans could exist on Mars, a subject that Elon Musk is adamant will happen by 2050? Lanza thinks not, and she is not very hopeful for a human colonisation, soon, or ever. “We already know a lot about the current Martian environment, and it’s not good for humans,” she says. “Besides the lack of atmospheric oxygen for humans to breathe, Mars lacks a protective magnetic field, which means that the surface radiation environment is relatively damaging for most terrestrial life.” She adds that there isn’t very much water on Mars, so it would take considerable effort to produce it from local materials. The anticipated returned samples come from the top six centimetres of the surface and so won’t be able to prove much about what could lie beneath. “All of this is to say that Mars sample return isn’t going to help us decide whether living on Mars is in our future, but it will give us considerable insight into our past by helping us understand how life does (or does not) arise on rocky worlds. And that’s exciting.”

In the meantime, Lanza is meteorite-hunting. She spent two months recovering them in Antarctica recently, as well as assisting with the next lunar mission, Artemis 3. It will see a female astronaut and a non-white person be part of the crew for a Moon mission for the first time in history, with the potential for them to be the first female and non-white Moonwalkers. Lanza thinks it is crucial to encourage a more diverse next generation of scientists. “You can’t be what you can’t see, I’ve seen that in my own life as a scientist. If you see women or people of colour being excellent, it tells you that you can do this.”

She also believes that engaging in outreach is a critically important part of her role. “My job is not about personal glory. It is all taxpayer-funded, so we need to tell people why they should care.”