'We are all Martians!': space explorers seek to solve the riddle of life on Mars
In the next few weeks, a flotilla of probes will be blasted into space from launch pads round the world and propelled towards one of the solar system’s most mysterious objects: the planet Mars. Within days of each other, spacecraft built by the USA, by China and by the United Arab Emirates will be sent on separate, seven-month voyages to investigate the red planet.
Never has so much interplanetary traffic been put en route to Mars at one time - and all of it is intended to help answer a question that has nagged scientists for decades: is there, or was there ever, life on Mars?
“Robot missions over the past decade or so have shown that Mars is not a dead, alien place as we had concluded in the late 20th century. In fact it is a world peppered with old lake beds, dried out river channels and organic material,“said Profesor Ray Arvidson, of Washington University, St Louis.
“In other words, back in the day, billions of years ago, Mars was warm and wet. Now we are going to find out if those conditions led to the evolution of life on Mars, just as they did on Earth, and to see if some of that life still persists underground.”
In every case, the spacecraft that make up the new Mars flotilla are highly ambitious in design and construction. The US mission - to be launched in early August - will involve dropping a van-sized robot rover called Perseverance into Jezero Crater, near an ancient river delta, in the Syrtis Major region of Mars. It will then examine rocks on the crater floor and collect samples which it will leave in caches to be collected, in several years’ time, by another - as yet unbuilt - robot rover.
The samples will then be placed in a rocket and blasted back to Earth in the hope of bringing around 500g of Martian soil and rock to researchers’ laboratories by 2031. These samples could reveal signs of past or even present Martian life.
In addition, Perseverance will carry a tiny robot helicopter, another first for Mars, and will also attempt to extract oxygen from the carbon dioxide in the Martian atmosphere - as a test of methods for supporting future human explorers of the planet.
Equally ambitious, the Chinese mission, Tianwen-1, is essentially a threein-one spacecraft consisting of a satellite that will orbit Mars, a lander, and also a rover that will travel across the Martian surface in search of water, ice and other features. China has recently developed considerable expertise in landing spacecraft and robot rovers on the Moon. Now it is scaling up its operations and is crossing interplanetary space to try out its hardware on
Mars.
Precise details of the Tianwen-1 mission are scarce, however. Its launch date and landing site on Mars have still not been revealed by the Chinese, for example, and most communications about the mission have been cryptic, to say the least. “Our team is working in the Wenchang launch centre right now, and everything goes smoothly,” was all Wang Chi, director-general of the National Space Science Center (NSSC) in Beijing, had to say about the project in an email to the journal Nature last week.
And finally there is the Emirates Mars Mission, or Hope as it is also known. It is scheduled for launch on Wednesday (15 July) on a Japanese H-2A rocket that will lift off from the Tanegashima Space Centre and is set to become the first interplanetary mission carried out by an Arab nation. The craft will enter Martian orbit in early 2021, marking the 50th anniversary of the birth of the United Arab Emirates, and will study, in detail, the atmosphere of the Red Planet.
The craft is fitted with an infrared spectrometer for studying Martian clouds and dust storms and ultra-violet detectors for analysing gases in the planet’s upper atmosphere. This data will then be combined and used to produce the first global weather map of the planet.
This mushrooming of Martian missions is remarkable, though the fact that these probes all have launch dates so near each other is also influenced by celestial mechanics, added Open University astrobiologist Susanne Schwenzer.
“Every 26 months, the orbits of Earth and Mars are aligned in a way that makes it relatively easy to send a rocket there,” she told the Observer. “These launch windows last only a few weeks and one is just about to open up - which explains why these different probes are being prepared for launch over such a brief period this summer.”
Blasting three separate probes to Mars is still an extraordinarily ambitious undertaking, however, particularly as these craft are being launched as our own world has been engulfed by an pandemic that has led to widespread suspensions and cancellations of many other scientific efforts. Indeed, had it not been for Covid-19, a fourth mission, a joint European-Russian probe, ExoMars, would have joined the robot fleet heading for the Red Planet this summer. However, it has now been postponed but will not be launched until 2022 when the next launch window for Martion missions opens up. Our interest in the Red Planet is going to continue for some time, it seems.
“There is no doubt that the exploration of Mars is going through a rebirth,” added Arvidson. “In the 1970s, the Viking missions to Mars revealed a world that appeared to be utterly dead and we stopped sending missions to the planet for a couple of decades. However, more recent probes have changed that view.”
These missions - which have included the US robot rovers Spirit, Opportunity and Curiosity - have shown that Mars must once have been lush and warm but was doomed as a cradle for complex life because of its size. The planet’s diameter is half that of Earth’s, which means it has a much smaller core at its heart compared with the one at the centre of our own planet. The Martian core, once molten, cooled and solidified billions of years ago while our larger core has remained hot and molten allowing convection currents within it to generate a magnetic field around the Earth.
And that is crucial. Without a molten core, Mars could no longer generate a magnetic field which had protected it from radiation from the Sun just as Earth’s magnetic field still shields us today. As a result, the Martian atmosphere and its surface water were swept away by this bombardment of solar particles and the planet became barren and hostile.
However, there is still a chance that life evolved there before the Mar