Jane Douglas, Tech & Gadgets Editor

Space: Could It Sustain Life?

What if climate change forced us to leave earth? What are the chances of us finding another life-supporting planet out there? Tech & Gadget's editor Jane Douglas delves deep into space to find the answers.

Is there anybody out there? (Image © AP Photo/NASA)

Our little planet boasts an ecosystem of enormous complexity and variety. This certain combination of temperature, terrain, vegetation, gravity and atmosphere (along with countless other variables) supports millions of species of creature – and us humans, obviously.

But if that certain balance of conditions was to be upset – by climate change or otherwise – could we find ourselves a suitable home anywhere else? Or is Earth the only planet with the right stuff to keep us alive?

Could we live in space? Join the debate

Lunar living

Our very closest option, the moon, isn’t the most welcoming of neighbours. Despite being the easiest of extra-terrestrial spots to reach, there’s no air to breathe once you get there (no atmosphere of any kind, in fact) and the temperature peaks above 100°C during the day and below 150°C at night.

Conditions as inhospitable as these don’t mean lunar living is impossible but making a permanent home there would demand considerable resources. Supplying breathable air and maintaining temperatures in the relatively narrow human-friendly range would only be for starters.

This image provided by NASA shows a color-enhanced image of the delta in Jezero Crater, which once held a lake. Two studies based on data from NASA's Mars Reconnaissance Orbiter have revealed that the Red Planet once hosted vast lakes, flowing rivers and a variety of other wet environments that had the potential to support life. (image © PA photos)

Some evidence suggests that there is water on the moon in the form of ice – though it’s not yet clear how much. We humans need a lot of that precious H2O to get by, and if Nasa’s 2009 Lunar Reconnaissance Orbiter tells us there’s not a lot of ice hidden away at the lunar poles, living on the moon gets more difficult still.

Anyway, if we’re looking for a place to sustain a substantial number of people – a kind of alternative Earth - then the moon is perhaps besides the point. It’s a dinky little rock, just one fiftieth the size of the Earth by volume.

Close to home

Moving beyond the moon, out towards the sun, the roughly Earth-sized Venus is not particularly inviting to a mass exodus of humans either. This planet features crushing pressures, roasting temperatures and some nasty clouds of highly corrosive sulphuric acid.

Mars, on other hand, looks a little bit friendlier. Further from the sun than Venus or Earth, the red planet averages a chilly – but not unmanageable – minus 50°C. Also good news: the Phoenix Mars Lander confirmed the presence of water (in ice form) in July and there might well be more in liquid form below the planet’s surface.

How we narrowly avoided an ice-age

Terraforming, the large-scale manipulation of a planet to fit human needs, is for now still the preserve of science fiction and academic speculation. Should it become a reality, however, and capable of tweaking Mars’ alien atmosphere into something more breathable, the colonization of Mars might become a serious possibility.

A view of planet Venus eclipsed by a thin crescent moon is seen in Hyderabad, India. (Image © Mahesh Kumar A/AP/PA Photos)

Discounting the sun’s nearest neighbour (Mercury, too hot by a long way) leaves us with four Solar System planets: Jupiter, Saturn, Uranus and Neptune. These are all gas giants and unlikely candidates for colonization – at least if we expect to live in a way that resembles life on Earth.

Saturn’s moon Titan, which uniquely boasts an atmosphere of its own, might present an option – but if we’ve settled on searching for a alternate Earth, a planet that can look after us in the way Earth does, then we should really be looking even further abroad, to planets beyond the confines of our own Solar System.

Extrasolar planets

Since the 1990s, more than 300 planets have been discovered orbiting distant stars. These ‘extrasolar’ planets are so remote, tiny and dark (compared to the huge bright stars they circle) that technology initially only allowed astronomers to detect very big planets – mostly gas giants, and all several times larger than the Earth.

The north polar ice cap on Mars taken by NASA's Mars Reconnaissance Orbiter where liquid water sustaining living organisms may be beneath the surface. (image © NASA/PA Photos)

As the hunt for smaller and more Earth-like planets continued, it turned up terrestrial (rocky) worlds merely a few times bigger than our home planet. The most promising of these so far is named Gliese 581 d.

Discovered last year, Gliese 581 d is a terrestrial planet 20 light years from Earth. It sits just on the edge of its sun’s ‘Goldilocks zone’ – that is, in the region that is at the right distance to be not too hot, not too cold. In fact, Gliese 581 d is on the ‘almost too cold’ edge of the Goldilocks zone, but scientists suspect that a natural greenhouse effect may turn up the planet’s heat just enough to give it a surface temperature that could allow liquid water to exist.

Finding life out there

New technologies have enabled astronomers to begin looking for signs of life on far-flung extrasolar planets – in the form of traces of water or organic molecules, for instance. The search also continues for hints of life closer to home – even now the Phoenix Mars Lander is still at work, determining whether microbial life ever arose on the red planet.

Is earth unique or could there by other planets out there that could sustain life?

But there has been no completely conclusive evidence of extra-terrestrial life so far. For now, we’re only sure of one kind of life in space: the small crew of humans aboard the International Space Station.

In search of the big bang: Hadron Collider special

Space travel

Pondering the colonization of Mars and hunting for Earth-like planets light years away is all very well, but with a mission to send just a few astronauts to Mars only tentatively scheduled in decades’ time, shipping large numbers of people to distant worlds is a long, long way off yet.

The kind of space travel technology that would make feasible trips to far-off Gliese 581 d (a 20-year journey even at the mind-bogglingly fast speed of light) is still the stuff of science fiction. It turns out that for the time being looking after our own planet might just be easier than making our way to an alternative one. Better make the most of what we’ve got – even while we’re looking to space for other options…

Further Reading

Could we live in space? Join the debate

In search of the big bang: Hadron Collider special

How we narrowly avoided an ice-age

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