Is there life on Mars? A new generation of explorers is putting that question front and centre like never before

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For modern-day adventurers, Mars is the future. It is the rust-coloured Everest in the sky that could one day reward a team of human explorers with the distinction of being the first to set foot on another planet.

Nathalie Cabrol sees it differently.

“Mars is our memory,” said Dr. Cabrol, who is director of the SETI Institute’s Carl Sagan Center for the Study of Life in the Universe, near Palo Alto, Calif.

“Imagine you are an orphan,” she said. “You never knew your parents. Where do you go to understand where you came from?”

For astrobiologists like Dr. Cabrol, the answer is Mars.

Whereas Earth’s history is forever being overwritten by volcanoes, glaciers, pounding waves and jostling continents, the surface of Mars offers a direct window on the past, with large swaths of the planet’s surface dating back more than 3.5 billion years. This corresponds to the early days of life on Earth, when colonies of microbes were thriving and evolving, setting the stage for the more complex ecosystems that were still to come. If something similar was taking place on Mars at the same time, when the solar system’s fourth planet was relatively hospitable compared with the frozen and nearly airless desert it has since become, then there is every chance that traces of life’s beginnings can still be found there.

That, in essence, is why NASA is launching Perseverance, an SUV-sized rover that is meant to touch down on the floor of a Martian crater next February and search for signs that the red planet was once a living world. It is not the only spacecraft making the voyage. On July 19, the United Arab Emirates sent a probe named Al Amal (”Hope”) to orbit Mars. Three days later, China successfully dispatched its first Mars mission, dubbed Tianwen-1 (”Questions to Heaven”), which includes an orbiter, lander and rover.

The flurry of launches has been called a new space race. But the timing has more to do with celestial mechanics. Because Earth and Mars orbit the sun at different rates, the optimal window for sending a spacecraft from one planet to the other only comes up every 27 months or so.

But while all three missions are carrying science instruments that can add to our knowledge of a surprisingly complex planet, Perseverance is the only one explicitly aimed at discovering whether or not there was once life on Mars. “Either way, it’s really profound in terms of how we see ourselves in the universe,” said Luther Beegle, deputy science manager at NASA’s Jet Propulsion Laboratory in Pasadena who leads one of the instrument teams on Perseverance.

Dr. Cabrol agrees. Our own existence proves that life is possible. Finding a second example, even if it has since died out, would address the question of whether life is abundant throughout the cosmos. “That’s the driving question of this mission,” she said. “And in some ways it’s the fundamental scientific question of our time.”

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MIRAGES TO MICROBES

Our fixation with Mars as the place to hunt for alien life emerged during America’s Gilded Age, when telescopes were finally large enough to magnify the subtle changes in brightness that had long been observed on the planet.

No Mars-watcher of the period was more ardent than Percival Lowell, a Massachusetts businessman-turned-astronomer who established Arizona’s Lowell Observatory in 1894. Like a proto Elon Musk, Lowell was bent on directing his earthly fortune toward celestial achievements. He was influenced by Giovanni Schiaparelli, an Italian astronomer who reported the presence of linear features on Mars that he dubbed canali. Translated into English, the term became “canals,” which suggested to Lowell that they were more than natural features.

Lowell convinced himself that he, too, could see canals on Mars. In his drawings he showed them connecting the polar reaches to darker areas near the equator, which he took to be oases of vegetation amidst a planet-wide desert. If so, the canals might be an elaborate irrigation system. “The most self-evident explanation … is probably the true one,” Lowell said in a lecture to the Boston Scientific Society. “Namely, that in them we are looking upon the result of the work of some sort of intelligent beings.”

Lowell’s theories about a Martian civilization were largely discounted by his academic contemporaries, but they stoked public fascination with the red planet. H.G. Wells famously picked up on this when he published his science fiction classic, The War of the Worlds, in 1898.

Lowell died in 1916 and the observatory he founded moved on to more conventional scientific projects. But while his notions of canal-building Martians were soon abandoned, the idea that a hardy form of plant life was eking out an existence on Mars persisted well into the 1950s.

But even this scaled-back version of Martian life would prove to be a mirage – or so it seemed in 1965, when an early NASA probe radioed back the first close-ups of Mars from space. The images showed a lifeless, cratered surface, far more like the moon than any place on Earth. Impressions shifted again six years later, when Mariner 9, the first spacecraft to orbit Mars, revealed a host of striking features, including giant volcanoes, breathtaking chasms and dry, sinuous channels that were highly suggestive of flowing water at some point in the past.

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The pinnacle of the first wave of Mars exploration came with the Viking missions: two NASA landers that set down on the Martian surface in the summer of 1976 and set about testing the soil for signs of microbial life.

The landers showed haunting colour images of the Martian landscape, with ochre soil and a salmon pink sky. But the biology experiments came up empty. The question of life on Mars shifted to the planet’s distant and apparently wetter past, but with no follow-up to Viking, there were no data to add to the story.

Twenty years had passed when a team based at NASA’s Johnson Space Center in Houston identified tiny structures in a meteorite that originated on Mars. The team announced that they had found what looked like microscopic fossilized bacteria. The claim caused a sensation.

“It immediately raised questions, both in the popular press and scholarly circles, that were not only scientific but also theological and social,” said Stephen J. Dick, NASA’s former chief historian and author of The Biological Universe.

He added that the find offered a hint of what would occur if Perseverance were to spot something suggestive of past life on Mars: “With the omnipresent social media these days, the announcement and reaction would spread like wildfire.”

Most experts have long since concluded that the fossil bacteria – like Lowell’s canals – can be chalked up to wishful thinking. But it was a lesson to scientists that if they hoped to avoid endless arguments over inconclusive evidence, the search for life on Mars demanded a more methodical approach.

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MAKING TRACKS

NASA returned to the surface of Mars in 1997 with a US$175-million lander that was a far cry from the billion-dollar Viking project. Yet the Pathfinder mission included a key step forward in the form of a small demonstration rover, called Sojourner, that tooled around its mother ship like a remote controlled toy. It was a promising reboot. Then NASA’s next two Mars missions failed disastrously, exposing the limits of administrator Dan Goldin’s directive to do planetary exploration “faster, better, cheaper.”

Wary of further failures, NASA took a step back and began designing a more robust and better resourced mission that would send a pair of solar-powered rovers to Mars in 2003. The roving duo, named Spirit and Opportunity, became the game changer. Built to last 90 days and travel 600 hundred metres each, the two rovers logged more than 20 years of mission time on Mars and covered nearly 50 kilometres between them.

The rovers’ scientific aims were more modest. To avoid overreaching on the question of part life, they were tasked only with documenting evidence for past water. By the time the next Mars rover, Curiosity, came along in 2012, that goal was upgraded to searching for signs of habitable environments – in other words, showing that Mars could have supported life at some point in its history. And while the rovers rolled on, NASA also sent two small landers, one in 2008 and one in 2018, to investigate separate questions related to the climate and interior of Mars. That brought the U.S. space agency’s count of successful Mars landings to eight. To date, no one else has managed one.

Now comes Perseverance, NASA’s biggest bet since the Viking era and the mission that is destined to renew the search for evidence of Martian life.

By all appearances, the spot that scientists have selected as the rover’s landing site is tailor made for the job. Jezero crater is a 45-kilometre-wide depression that was once a deep lake. Its most intriguing feature is a river delta where water rushed into the crater from the ancient highlands nearby. The crater therefore offers a place where water may have lingered at the surface for hundreds of thousands of years, but also one where rocks and sediment from a much wider catchment area have been deposited in one location.

“I think the site is superb,” said Dr. Cabrol, who was previously involved in the site selection for the Spirit rover, which also landed on a former lake bed. What makes Jezero different, she said, is the delta, a tantalizing feature that is challenging to navigate and would have been considered too much of a hazard for earlier missions.

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Chris Herd, a planetary scientist and meteorite expert at the University of Alberta, is part of the team that will help identify where the rover should look once it’s arrived. Among the most intriguing details he and his colleagues hope to investigate are the channels carved into the delta where layers of sediment can be seen from orbit.

“We’re pretty confident that we can drive up the toe of the delta and investigate those layers,” he said.

Unlike previous missions, the goal of Perseverance is not simply to investigate what Mars has to offer in situ, but to drill for small core samples of rock that can be cached and brought back for researchers to study in detail on Earth.

“Then you’ll be able to unleash the power of all those laboratories,” said Abigail Allwood, another Perseverance instrument team leader who is known for her work identifying the earliest accepted evidence of life on Earth in the rocks of her native Australia.

The challenge for the scientists guiding the rover, she said, is not just to look in the right place but to understand the context of what they are seeing so that the 43 sample tubes the rover will carry to Mars are filled with the most promising specimens possible.

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COSMIC QUEST

Since Pathfinder, 23 years ago, NASA’s Mars program has unfolded against a backdrop of new developments related to the search for life in the universe. The number of planets discovered in orbit around other stars has grown from a handful to thousands, including some that could have conditions favourable to life. Last week, the European Southern Observatory released the first direct image of a multiplanet system. In our own solar system, evidence is building for the existence of hidden reservoirs of water beneath the surfaces of some of the icy moons of the giant planets. On Enceladus, a small moon of Saturn, the Cassini spacecraft spotted plumes of water vapour shooting out of cracks near the moon’s south pole and later detected traces of salt and organic molecules mixed in with the water. All of this hints at the possibility that Enceladus could play host to micro-organisms right now, not just in the distant past.

In Canada, the new discoveries have prompted a collaboration between astronomers and experts who study the origins of life on Earth. The group has announced its intention to compete for funding under a new federal program designed to foster interdisciplinary projects.

“It will help us branch away from just looking for Earth-like planets … and ask whether the vast majority of planets that are unlike Earth are potential laboratories for biology,” said Jason Rowe, an astronomer at Bishop’s University in Sherbrooke, Que., who is leading the effort.

But none of this diminishes the allure of Mars as a target for astrobiology, in part because at the scale of a microbial colony – a hot spring, a clay deposit, a crack in a rock – it so closely resembles what scientists expect was present on the early Earth.

“Mars will always be a special place,” said Dr. Cabrol, who has joined the Canadian astrobiology collaboration as an international partner. “It’s the closest we have.”

She added that her greatest worry about Perseverance is that it will be unable to discover more about Mars than its predecessors. “It’s a distinct possibility,” she said.

In the end, it will depend on what there is to find. And even if nothing turns up, it’s unlikely the search will end there.

“I think we have reached a turning point where even the disappointment of not finding life or past life on Mars would not necessarily put a damper on Mars exploration,” Prof. Dick said. “Science wants to know the answer, as do all curious people, and so the exploration will continue.”

visual guide

The Perseverance project, step by step

Three countries – China, the United Arab Emirates and the United States – are sending spacecraft to Mars this year. NASA’s Perseverance rover is the most ambitious. It will search for signs of past life and collect samples for return to Earth at a later date

THE JOURNEY

The seven-month flight path minimizes travel time for all three probes. Perseverance is set to land on February 18, 2021. The UAE and Chinese missions will enter orbit around Mars in February and China will send its lander down a few months after that

Mars at arrival

Flight

trajectory

1.335 AU

1.567 AU

Earth at

arrival

1 AU*

The Sun

Earth at

launch

Mars at

launch

*The astronomical unit (AU), a measure of distance, is approximately the average distance between the Earth and the Sun, about 149.6 million km.

THE LANDING

Because of the signal delay between Earth and Mars, Perseverance is designed to guide itself safely down to the surface with an automated navigation system

TERRAIN-RELATIVE

NAVIGATION

1

Camera takes pictures as rover descends

2

Computer compares these to maps of area and adjusts flightpath to avoid hazards

3

Lander lowers rover as close as possible to target site

THE DESTINATION

Jezero Crater was once a deep lake. It features an ancient river delta where Perseverance can explore layers of sediment before moving on to the crater rim

JEZERO

CRATER

45km

THE ROVER

Perseverance is outfitted with a suite of cameras and other instruments. It can drill into Martian rock and cache the core samples for later collection by a follow up mission

INGENUITY

Drone-like helicopter carried on rover’s belly will demonstrate first powered flight on another planet

THE LEGACY

More than 30 spacecraft have been sent to Mars, starting with the first attempt by the Soviet Union in 1962. Several have imaged Mars from orbit but only eight have carried out missions on the planet’s surface. If successful, NASA’s Perseverance and China’s Tianwen-1 will make nine and ten.

Probe type and duration active on the surface:

Lander

Rover

Hybrid mission

Tianwen-1

Perseverance

InSight (active)

Curiosity (active)

Phoenix

Opportunity

Spirit

Pathfinder/Sojourner

Viking 2

Viking 1

1980

1990

2000

2010

2020

MURAT YÜKSELIR / THE GLOBE AND MAIL,

SOURCE: NASA; GRAPHIC NEWS

Three countries – China, the United Arab Emirates and the United States – are sending spacecraft to Mars this year. NASA’s Perseverance rover is the most ambitious. It will search for signs of past life and collect samples for return to Earth at a later date

THE JOURNEY

The seven-month flight path minimizes travel time for all three probes. Perseverance is set to land on February 18, 2021. The UAE and Chinese missions will enter orbit around Mars in February and China will send its lander down a few months after that

Mars at arrival

Flight

trajectory

1.335 AU

1.567 AU

Earth at

arrival

1 AU*

The Sun

Earth at

launch

Mars at

launch

*The astronomical unit (AU), a measure of distance, is approximately the average distance between the Earth and the Sun, about 149.6 million km.

THE LANDING

Because of the signal delay between Earth and Mars, Perseverance is designed to guide itself safely down to the surface with an automated navigation system

TERRAIN-RELATIVE

NAVIGATION

1

Camera takes pictures as rover descends

2

Computer compares these to maps of area and adjusts flightpath to avoid hazards

3

Lander lowers rover as close as possible to target site

THE DESTINATION

Jezero Crater was once a deep lake. It features an ancient river delta where Perseverance can explore layers of sediment before moving on to the crater rim

JEZERO

CRATER

45km

THE ROVER

Perseverance is outfitted with a suite of cameras and other instruments. It can drill into Martian rock and cache the core samples for later collection by a follow up mission

INGENUITY

Drone-like helicopter carried on rover’s belly will demonstrate first powered flight on another planet

THE LEGACY

More than 30 spacecraft have been sent to Mars, starting with the first attempt by the Soviet Union in 1962. Several have imaged Mars from orbit but only eight have carried out missions on the planet’s surface. If successful, NASA’s Perseverance and China’s Tianwen-1 will make nine and ten.

Probe type and duration active on the surface:

Lander

Rover

Hybrid mission

Tianwen-1

Perseverance

InSight (active)

Curiosity (active)

Phoenix

Opportunity

Pathfinder/Sojourner

Viking 2

Viking 1

1975

1980

1985

1990

1995

2000

2005

2010

2015

2020

MURAT YÜKSELIR / THE GLOBE AND MAIL,

SOURCE: NASA; GRAPHIC NEWS

Three countries – China, the United Arab Emirates and the United States – are sending spacecraft to Mars this year. NASA’s Perseverance rover is the most ambitious. It will search for signs of past life and collect samples for return to Earth at a later date

THE JOURNEY

The seven-month flight path minimizes travel time for all three probes. Perseverance is set to land on February 18, 2021. The UAE and Chinese missions will enter orbit around Mars in February and China will send its lander down a few months after that

Mars at arrival

Flight

trajectory

1.335 AU

1.567 AU

Earth at

arrival

1 AU*

The Sun

Earth at

launch

Mars at

launch

*The astronomical unit (AU), a measure of distance, is approximately the average distance between the Earth and the Sun, about 149.6 million km.

THE LANDING

Because of the signal delay between Earth and Mars, Perseverance is designed to guide itself safely down to the surface with an automated navigation system

TERRAIN-RELATIVE

NAVIGATION

1

Camera takes pictures as rover descends

2

Computer compares these to maps of area and adjusts flightpath to avoid hazards

3

Lander lowers rover as close as possible to target site

THE DESTINATION

Jezero Crater was once a deep lake. It features an ancient river delta where Perseverance can explore layers of sediment before moving on to the crater rim

Rover path

Search Spots

River canyon

Carved by water which flowed through crater rim 3.5 billion years ago

JEZERO

CRATER

45km

DELTA

Crater rim

Shoreline of

former lake

Landing

site

Edge of delta

Ancient lake bed

THE ROVER

Perseverance is outfitted with a suite of cameras and other instruments. It can drill into Martian rock and cache the core samples for later collection by a follow up mission

POWER SUPPLY

Relies on the decay of radioactive plutonium to generate electricity

SUPERCAM

Can fire a laser to illuminate rocks and study mineral composition from several metres

SHERLOC

Ultraviolet spectrometer searches for organics and minerals

RIMFAX

Ground-penetrating radar to map geology beneath surface

MASTCAM-Z

Advanced camera

MEDA

Weather station

PIXL

X-ray spectrometer to identify chemical elements

MOXIE

Experiment to demonstrate how astronauts might produce oxygen from Martian CO2 for breathing and fuel

INGENUITY

Drone-like helicopter carried on rover’s belly will demonstrate first powered flight on another planet

THE LEGACY

More than 30 spacecraft have been sent to Mars, starting with the first attempt by the Soviet Union in 1962. Several have imaged Mars from orbit but only eight have carried out missions on the planet’s surface. If successful, NASA’s Perseverance and China’s Tianwen-1 will make nine and ten.

Probe type and duration active on the surface:

Lander

Rover

Hybrid mission

Tianwen-1

Perseverance

InSight (active)

Curiosity (active)

Phoenix

Opportunity

Spirit

Pathfinder/Sojourner

Viking 2

Viking 1

1975

1980

1985

1990

1995

2000

2005

2010

2015

2020

MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE: NASA; GRAPHIC NEWS