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Is there life on Mars? It鈥檚 a question people have been pondering since long before David Bowie wrote his iconic song.

As planetary geologists, and might very well help in finding the best places on the red planet to hunt for it.

Campbell is a professor and Ukstins a senior lecturer at the University of Auckland鈥檚 . Before they began considering Mars geology, both started their careers examining rocks Earthside. Actually, they never stopped, in part because some of Earth鈥檚 most extreme environments are good analogues for Mars.

Today, Mars is, if not quite a dead planet, then a geologically inactive one with very little atmosphere. Extremely cold, windy and dusty, with low atmospheric pressure and no liquid water, it鈥檚 not a place where humans could survive without heavy protection.

鈥淧robably not the best place to go on vacation,鈥� says Ukstins.

Early Mars, however, was different. About four billion years ago, when the Earth too was young, Mars was very geologically active, with a lot of volcanoes 鈥� in fact, it still boasts the tallest known volcano in the solar system, Olympus Mons. In those ancient times, the core of Mars, like Earth鈥檚, was liquid, and its movement produced a magnetic field. Earth鈥檚 magnetic field is what keeps our atmosphere in place around the planet and protects us from solar radiation, says Ukstins.

With all that volcanism churning out gases, early Mars probably had an atmosphere not unlike ours, if thinner. There is also significant evidence that there was liquid water on the surface early in Mars鈥檚 history 鈥� including giant floods, says Ukstins.

One of the branches of Ukstins鈥� research centres on examining rocks 鈥� their composition, their weathering patterns and their distribution 鈥� in extreme environments on Earth. The objective is to figure out what the climate may have been like early in Mars鈥檚 history.

You鈥檙e probably familiar with photosynthesis, the process by which plants take sunlight, water and carbon dioxide and convert it into glucose and oxygen. Almost all life on Earth relies on photosynthesis directly or indirectly. But there are exceptions in extreme environments.

Deep on the ocean floor, where sunlight doesn鈥檛 penetrate, life thrives around hydrothermal vents 鈥� undersea hot springs 鈥� and cold methane seeps, where methane gas bubbles up from below the sea floor. Specialised microbes can convert the chemicals bubbling up from the Earth鈥檚 crust into energy, a process known as chemosynthesis. Other deep-sea organisms get their energy by eating the microbes or by allowing them to live symbiotically within them.

鈥淭hese kinds of extreme environments tell us a lot about what life might have been like when it first evolved on Earth, because we didn鈥檛 have any oxygen then and the only living creatures were microbes,鈥� says Campbell. 鈥淭hey might even have been the places where life originated here on Earth.鈥�

As a graduate student, Campbell studied fossil methane seeps 鈥� in fact, she discovered one of the first worldwide, on the U.S. West Coast. One day, at a conference where she鈥檇 talked about her research, a man introduced himself. His name was Jack Farmer and he worked at NASA.

鈥淗e asked, 鈥楢re there any signs of fossil microbial life in those ancient methane seeps you鈥檙e working on?鈥� I said yes. He said, 鈥楥ome to NASA and do a postdoc with me.鈥欌��

Ultimately, Campbell and Ukstins would like to be involved in a Mars rover expedition to look for fossilised signs of life on Mars.

Campbell has gotten tantalisingly close. A U.S. colleague of hers, Steve Ruff of Arizona State University, was involved in the Spirit mission, which was active from 2004 to 2010. At a site called Columbia Hills, it found finger-like silica mineral growths protruding above the Martian soil, a likely indication of past hot springs.

However, without the ability to return samples to Earth for scientists to examine, the discovery resulted in more questions than answers.

 In 2010, Spirit got stuck in Martian sand and the mission ended. However, NASA had plans for more rovers. Importantly, NASA was also developing a proposal for a mission that would search for signs of past life and, for the first time, return samples to Earth.

鈥淪teve said, 鈥榊ou should be on our team proposing to go back to Columbia Hills,鈥欌�� says Campbell. 鈥淪o in 2017, I joined the international group of researchers answering the call for proposals for NASA鈥檚 Mars 2020 landing site selection and sample return mission.鈥�

Campbell and Ruff鈥檚 team鈥檚 proposal ended up being one of the final three in contention. However, NASA ultimately decided it did not want to go back to a site it had already explored. NASA now has two rovers, Curiosity and Perseverance, exploring Mars, though not at the Columbia Hills site. Perseverance is caching samples for future return. China also has a rover on Mars, Zhurong.

If New Zealand does get involved with a future Mars mission, it would inspire a future generation of scientists and engineers and put New Zealand's space sector on the world stage. What's more, Ukstins鈥� and Campbell鈥檚 geological expertise could help a rover operate better.

Not only did Spirit get stuck in sand, leading to its demise, NASA鈥檚 most recent Mars rover, Perseverance, has run into difficulties with rock sampling. Its first attempt to collect a sample resulted in surprisingly soft, crumbly rock that didn鈥檛 make it into the collection tube.

There are people who test rovers in environments on Earth that are good analogues for Mars. Ukstins has been involved in some of that work in Chile鈥檚 Atacama Desert. There, while participating in prototype testing, she noticed that scientists looking at rover photos were classifying shiny black rocks as 鈥渨hite rocks鈥� because of sun glare and the lack of a UV filter on the camera.

鈥淭his highlights the importance of testing every system thoroughly before you get to Mars and it鈥檚 too late,鈥� says Ukstins.

• 鈥� Kathy Campbell is chair of a network that focuses on research, education and public outreach in astrobiology, an interdisciplinary field that asks big questions such as where life started and if we鈥檙e alone in the universe.
• 鈥� A new, transdisciplinary University of 撸撸视频course for students of all majors, exploring life and its extent, from galactic to microbial realms.