A lake on Mars? Don't pack snorkels in the space ship quite yet
Nasa’s chief scientist explains what a newly found Martian ‘lake’ means, and why it may not exist at all
There is nothing new under the sun — or on Mars. Even with the announcement last week of the discovery of underground water on the Red Planet, one way or another, we have been here before.
“Water on Mars is not a novel idea,” says Dr James B Garvin, chief scientist of Nasa’s Goddard Space Flight Center near Washington DC. He reminds me that Mars was long thought to be a parched wasteland where aeons ago oceans perhaps lapped against ancient shores ... until 2008, that is, when Nasa’s Phoenix Lander detected a layer of water. And then, just a few years later, a Nasa orbiter circling Mars overhead discovered thawing ice deposits on mountain slopes.
Where there’s ground ice, there’s the possibility of liquid water, and where there’s the possibility of liquid water, the conditions exist for life, however primitive. The past decade, then, has been something of a race to find signs of that life on Mars.
So last week, when an Italian team of researchers published their article Radar Evidence of Subglacial Liquid Water on Mars in the journal Science, Garvin was anything but surprised about evidence suggesting a large underground lake —two kilometres across or more — trapped below the ice of the south pole. Not only that, but the team behind the article opined that “there is no reason to conclude that the presence of subsurface water is limited to a single location”.
Could it be true? At first blush, this news appears to be a confirmed finding, the unassailable result of three-an-a-half years of soundings performed by a European spacecraft, Mars Express, between 2012 and 2015. At Nasa, however, Garvin and others are not wholly convinced.
“The Italians are all smart dudes,” he concedes, but says their results are far from definitive. They’ve detected something “stretching maybe a mile or more”, and it may be liquid water. “If you shine radar at water, it would be 40 times brighter than its surroundings. But this is only three times.”
Scientists are agreed that this is an “exciting anomaly” that might point to a buried Dead Sea on Mars — but it also could be sand or silt with some liquid between the grains, or even perchlorate, a “super-salt” capable of melting stubborn Martian ice. In that case, the subterranean “lake” might not be water at all, just a salty deposit.
Garvin’s caution stems in part from Nasa’s hesitancy to oversell discoveries. In 1984, the agency revealed with great fanfare the discovery of possible microfossils in a Martian meteorite collected here on Earth. The announcement seemed for a time to herald a new Age of Aquarius. This bit of ancient rock, called ALH8001, looked to be a time capsule hurled in our directed from Mars containing an amazing secret, that Mars once harboured forms of microbial life, and perhaps even more complex life forms – and might still do so.
On further examination, doubts were raised. The meteorite had been lying on Earth on the slopes of the Alan Hills in Antarctica for quite some time, and had perhaps had become contaminated with life on ... Earth. It became difficult to prove that it contained a pristine sample of extraterrestrial life. Maybe we were just looking at ourselves. Thirty-five years later, ALH8001 still has its proponents, but scientific consensus about what, exactly, it contains, or means, no longer exists.
Today, the most Garvin will say is that the “lake” — if that’s what it is — “could be a source of microbial life”.
The ability to study other planets has set in motion a revolution in thinking about planetary geology, a revolution not unlike that kickstarted by Galileo, or other scientists studying natural phenomena. These observers see the same things as their scientific forebears, Aristotle, for instance, but they interpret them differently. It can lead scientists down unusual speculative pathways.
Garvin, a planetary geologist, wonders aloud if Mars somehow “follows playbooks different from ours”. And he asks: “How do you use terra-centric standards to look for signs of life, as agnostics tend to do? It raises the bar on ‘weird’ life on Mars being able to find a way to exist.” Even the definition of “life” is up for grabs. And perhaps life on Mars, or elsewhere, differs in some important respects life on Earth. If we don’t recognise it as such, is it still life?
Elon Musk, the inventor, engineer and self-promoter, is keen to find out. Musk has already announced that SpaceX, the aerospace company he founded just 16 years ago, plans to send a test vehicle to Mars as early as the first half of 2019.
But to Musk, the hazards function mainly as incentive, if only to prove that he can overcome them. In addition to the requirements of rocketry, and training a crew, just getting to Mars is a formidable undertaking. At its closest approach, Mars is 54 million kilometres away. With the average distance between Earth and Mars coming in around 225 million kilometres getting to the Red Planet would mean a journey of at least six months.
As Garvin puts it: “Musk wants to pioneer the Martian frontier. The problem is, physics isn’t free.” By which he means, as well as the distance and danger involved, there’s the immense expense.
Garvin compares exploring that underground “lake” on Mars to the difficulties of exploring on Earth: “Let’s say this lake is a mile below the surface ... well, drilling that distance below the surface of the Earth costs a great deal. But drilling down a mile on Mars would tax the entire world economy, for an uncertain benefit.”
Rather than looking for life on Mars, perhaps there’s something to be said for improving life on Earth.
– © The Sunday Telegraph