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Roula Khalaf, Editor of the FT, selects her favourite stories in this weekly newsletter.
The writer is a science commentator
Another piece of the Martian puzzle is slotting into place. The surface of the Red Planet is laced with grooves and channels, long seen as souvenirs of an ancient watery past.
Now there is evidence that our planetary neighbour, already known to have ice at the poles, harbours liquid water beneath its surface.
On Monday, researchers in the US revealed they had seen seismic signals indicating a water reservoir buried deep below the crust. In terms of volume, it is not so much a puddle but an infinity pool, enough to cover the entire planet with an ocean at least one kilometre deep.
Given that liquid water is a prerequisite for life as we know it, the underground reservoir, which could be as far as 20km below the surface, will become an obvious destination to look for life. The revelations will also lend renewed impetus to future crewed missions to Mars, which Nasa hopes to achieve by the 2030s.
The prospect is a mixed blessing: we have a moral duty to look for life next door, if it exists, but discovering it will also bring an obligation to shield it from the worst piratical instincts of our own species.
The data was collected by Nasa’s InSight lander, which touched down on Mars in 2018. Over the next four years, its seismometer recorded the planet’s vibrations and rumblings, called “Marsquakes”, as well as picking up signs of meteor impacts. A team led by Vashan Wright, at the Scripps Institution of Oceanography in San Diego, ran the signals through the kind of mathematical model used to map underground aquifers and oilfields.
Their brief paper, published on Monday in the Proceedings of the National Academy of Sciences, contains a knockout conclusion: “A mid-crust composed of fractured igneous rocks saturated with liquid water best explains the existing data.”
Planetary scientist Ian Crawford of London’s Birkbeck University, who was not involved in the research, said that confirming the presence of a subsurface aquifer will most probably require a new mission equipped with dedicated geophysical instruments.
With abundant evidence of a sculpted landscape, the whereabouts of Martian water has been a long-standing enigma. There is water ice at the poles and traces of water vapour in the atmosphere but that is not regarded as enough to account for what once flowed. One theory is that the liquid water disappeared when Mars lost its atmosphere around three billion years ago.
This latest finding suggests at least some percolated down into the crust. It is not far-fetched to imagine this watery underground kingdom of cracks and crevices hosting a form of microbial life, akin to the “extremophiles” found on Earth. Hardy lifeforms thrive in the unlikeliest terrestrial niches, from the driest deserts to the superheated, high-pressure acidic neighbourhoods of undersea volcanic vents.
Michael Manga, a team member based at University of California, Berkeley, says: “I don’t see why [the underground reservoir] is not a habitable environment . . . deep, deep mines [on Earth] host life, the bottom of the ocean hosts life. We haven’t found any evidence for life on Mars, but at least we have identified a place that should, in principle, be able to sustain life.”
Chemists at Tufts University in Massachusetts have previously shown that bacteria, including E-coli, can be grown on Martian regolith (the loose material on its surface) in the presence of water.
Accessing the Martian aquifer, though, presents an unearthly challenge: it is thought to lie somewhere between 12km and 20km below the surface.
That turns the search for extraterrestrial life into an engineering problem. Russia and China, both spacefaring nations with a penchant for flexing technical credentials, have the upper hand here.
Russia has already dug down vertically to more than 12km on Earth, creating the Kola Superdeep Borehole in the north-west of the country. China is currently drilling an 11km borehole in the Tarim basin, in Xinjiang. The hole, called Shenditake 1, will be used to search for oil and gas and study the evolution of the Earth.
Elon Musk would surely love to be boring on Mars. The prospect of a water source will energise those, like the brash tech titan, who dream of colonising and controlling the Red Planet without restraint. But the game has changed, given the increased possibility that Martian life, however basic, might exist.
That demands a spirit of exploration rather than exploitation: continuing the search for life beyond our own planet while treading lightly as we go.
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