Mars, the fourth planet in our solar system is about half the size of Earth – around 4,220 miles in diameter – and has two moons, named “Phobos” and “Deimos”.
Temperatures range from minus 140 degrees Celsius to plus 30 degrees Celsius. Gravity is about 62.5 percent less than what we’re used to here on Earth. And the planet’s atmosphere is composed almost entirely of carbon dioxide – 96 percent.
Professor of Astrophysics, Chris Lintott, describes it as a “horrible place.”
“It’s drier than the driest desert on Earth, there’s hardly any atmosphere to speak of,” he says.
“There is a thin one, but you certainly couldn’t breathe it. And the place is dusty, the surface is made of sort of red, rusty sand, you could think of it as. And there are winds in that thin atmosphere that could whip up the dust, and it gets everywhere.”
In recent years, scientists from NASA and Europe have honed their research skills by studying the Australian outback, home to some of the oldest fossilized life forms.
Scientist Susanne Schwenzer, who’s worked on NASA’s Opportunity rover, compares Mars to Chile’s Atacama Desert.
“Around me in the background, there are lots of green plants, right now, you wouldn’t see any of that. All you would see is rocks and sand. It is a very dry place, like, for example, the Atacama (Desert) on Earth,” she says.
“And it’s even more dry because of the thin atmosphere. And it’s cold. At night, temperatures fall to minus 30 or even minus 50 degrees (Celsius), depending on the season.”
Our planetary neighbor has been a popular target for exploration, with rovers on its surface and other probes examining the planet from orbit.
Mankind’s understanding of the red planet has evolved hugely since NASA’s Mariner 4 spacecraft first took photos of Mars back in 1964.
Researchers back then saw nothing more than a “cold, barren” planet.
Scientists have been seeking organic molecules on Mars ever since the 1976 Viking landers. The twin Vikings came up pretty much empty.
NASA’s Opportunity rover, pronounced dead in February last year, after 15 years roaming the red planet, was a robotic geologist, equipped with cameras and instruments at the end of a mechanical arm for analyzing rocks and soil.
Its greatest achievement was discovering, along with its identical twin rover Spirit, evidence that ancient Mars had water flowing on its surface and might have been capable of sustaining microbial life.
The notion of water on Mars has long fascinated scientists because of the possibility that the planet may have once harbored similar conditions to those that allowed life to develop on Earth.
“When we flew past Mars with the Mariner 4 spacecraft in 1964, it looked just barren, dry, some impact craters because we didn’t have the resolution to look at all the details,” says Schwenzer.
“It’s only since the Spirit and Opportunity rovers that we understand the geology and the rocks of Mars a lot better. So we know that these rocks contain elements such as iron, calcium, magnesium, which are really important to make an environment.”
Scientists now believe Mars was once very different to how we see it today, perhaps even similar to Earth.
Patches of ice previously spotted on Mars provide tantalizing hints of a watery past for the arid world.
“We can assume that Mars once had a thicker atmosphere, we can see evidence, obviously geological evidence on the surface of Mars, that there was water flow,” says Lucinda Offer, executive director of The Mars Society, an advocacy group dedicated to the human exploration and settlement of the red planet.
“So, we can at least imagine that Mars once had water on it.”
In recent years, new Mars discoveries have advanced the case for possible life on the red planet, past or even present.
NASA scientists reported their Curiosity rover had found potential building blocks of life in an ancient lakebed.
The organic molecules preserved in three billion-year-old bedrock suggest conditions at Mars may have once been conducive to life.
Curiosity also confirmed seasonal increases of methane in the Martian atmosphere. Researchers say they can’t rule out a biological source.
“The question is, given that all the ingredients existed, did life get started?” asks Lintott.
“We know that it did on Earth. Finding out whether it did on Mars is the next big question.”
Scientists agree more powerful spacecraft – and, ideally, rocks returned to Earth from Mars – are needed to prove whether tiny organisms like bacteria ever existed on the red planet.
But what might the presence of life on Mars mean for potential crewed missions to the red planet?
“If we find life on Mars, what’s the decision we’re going to make? Do we go there because we want to protect it?” asks Offer.
“China’s looking for life, India will be looking for life, NASA is definitely looking for life, and ESA (European Space Agency) is going to be looking for life. That’s a lot of countries looking for life. And if we do find life there, we’re gonna have to ask ourselves those big questions.”
Scientists from the United Arab Emirates, China and the U.S. will be hoping to answer more questions when their missions takeoff for Mars later this month.