Wednesday's headline-making announcement from Italian scientists about a possible lake underneath the Martian south pole adds to a growing list of other worlds we believe have liquid water. But it also adds to a deepening mystery about what it all means – especially to us on this lonely Blue Planet teeming with life and strife.

About 70 percent of Earth’s surface is covered by water, most of it in oceans. The rest is found in rivers, lakes, frozen in glaciers, and inside the bodies of every known plant, animal, and micro-creature on the planet.

Life, it appears, is not possible without H2O – and for good reason. Among its many unique properties, water is an extraordinary solvent that greases the wheels of life’s biological machinery.

It’s exciting, therefore, whenever we discover evidence for liquid water “out there” somewhere. For instance, beneath the surfaces of Jupiter’s moon Europa or Saturn’s moon Enceladus, whose phenomenal geysers shoot more than 100 miles into the air. Some research suggests even lowly Pluto – demoted in 2006 to the status of a dwarf planet – harbors subterranean pockets of water, kept fluid by tidal forces from its five nearby moons.

Above all, there’s our storied neighbor Mars. It has polar caps – both north and south – made of regular and dry ice (i.e., frozen carbon dioxide). It also has surface features that look a lot like dry river beds, suggesting the elixir of life once flowed abundantly and freely there.

And now this latest headline: bright reflections detected by the European Space Agency’s Mars Express, a ground-penetrating-radar-equipped spacecraft that’s been orbiting the Red Planet since 2003. The Italian scientists interpret the signals to mean there’s a twelve-mile-wide lake of salty water several feet deep sloshing around one mile beneath the Martian surface.

Surely, this now raises the possibility that, at the very least, Little Green Microorganisms dwell there. After all, exotic, insanely hardy, methane-eating bacteria live in sub-glacial lakes in our own Antarctic.

Ah, if only it were that simple.

For starters, the inferred lake beneath the Martian south pole might be nothing more than an aquiver of sludge. Both brine and sludge produce bright radar signatures.

It’s also possible the reputed lake is just an optical illusion. NASA’s Mars Reconnaissance Orbiter, which is also equipped with ground-penetrating radar, has been circling Mars since 2006 and sees no reflections implying the existence of a subterranean lake.

Even if the announcement is substantiated by future missions – and I personally hope it is – water is not a smoking gun. Where there’s water, there’s not necessarily life.

Still, every alleged discovery of water on other worlds represents an invaluable experiment that tests the veracity of biology’s current notions about how life came about on Earth. If we keep racking up evidence for water out there, but no life, it will deal a serious blow to the belief in abiogenesis – that life arose from scratch in a primordial soup of ordinary, inorganic chemicals. That would be a big headline.

If, however, we do find life inhabiting far-flung, water-borne venues, it will strengthen the abiogenesis thesis. That, too, would be a huge headline.

It’d also be a very sobering one. Why? Because, if water and life do prove to be abundant throughout the cosmos, then we’ll be forced to ask: “Where, then, is everyone??”

It’s a question I addressed in a recent opinion piece and that leads to many disquieting possibilities. One of them is this: simple water-borne organisms that develop into complex, intelligent life forms inevitably self-destruct.

The late writer and futurist Sir Arthur C. Clark had that possibility in mind when he stated, “It has yet to be proven that intelligence has any survival value.”

With every passing year in our search for extraterrestrial water and life, we are getting closer to finding, if not outright proof, then a resolution to Clark’s assertion.

Is intelligence ultimately a blessing or a curse? Surely, the answer will make for the biggest headline of all.