The Economist explains

The significance of liquid water on Mars

There could be an ocean’s worth deep underground

Photograph: NASA

THE APPLICATION of Bayesian inversion to a range of lithologic parameters in an assessment of seismic data hardly seems the stuff of headlines. But when the seismic data you are assessing come from Mars, and when your reasoning suggests that the best explanation for them is liquid water in the pores between rocks, you have a story. There is little people thirst for more, when it comes to planetary science, than water on Mars. Why does the prospect provoke such excitement—and what does this new research add to the story?

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