Why Us, And Not Them?

In 1877, when the Italian astronomer, Giovanni Schiaparelli, peered through his telescope, on the roof of the Palazzo di Brera, in Milan, he believed, what he saw on Mars, was an elaborate grid of canali (Italian for “channels” or “grooves.”)

That got translated into English as “canals,” a word with a clear connotation of design, of vast engineering works, constructed for a purpose. His successors enthusiastically took up the notion, and some like Percival Lowell, even went so far as to identify Mars’ capital.

When NASA’s Mariner 4 swung past the planet’s northern hemisphere in 1965, and sent back a series of grainy, black-and-white photographs, they confirmed that there were no such structures.

The search for life on Mars is now in its sixth decade. In the The New Yorker piece, “The Martian Chroniclers,” Burkhard Bilger writes:

Forty spacecraft have been sent there, and not one has found a single fossil or living being.

Still, we keep going back. Like a delinquent sibling, Mars is all we’ve got—the next Earth-like planet may be in the Tau Ceti system, seventy trillion miles away—and its virtues nearly redeem its vices.

By comparison, Mars is a mere stone’s throw away.

On November 26, 2011, NASA sent the world’s most sophisticated mobile science laboratory to explore it: the robotic rover, Curiosity. The latest planetary exploration vehicle sent by NASA was “five times as large as its predecessors—an S.U.V. to their golf carts.” It took 10 years to build, and cost $2.5 billion. More than 7,000 people had worked on it.

It was sent with lowered expectations: to just look for places that once might have been habitable. Its mission directive is to explore Mount Sharp, a 3.5-mile-high peak that stands in the middle of the Gale Crater, its destination on Mars. Even lifeless, Mars may answer some very old questions about life.

What’s remarkable about this mountain is that there’s none like it on Earth.

On Earth, mountains form when sections of the planet’s crust—tectonic plates—either collide and slide over each other or when magma from below spills over onto the surface.

But Mars has no tectonic activity. So, how did this mountain form? From the layer-by-layer buildup of sediments, laid down after a massive asteroid strike hollowed out Gale Crater. Its strata offer a textbook on Martian prehistory.

Like fraternal twins, [Mars and Earth] were born at the same time, about four and a half billion years ago, and took roughly the same shape.

Had an alien astronomer swiveled his telescope toward them in those days, he might have found them equally promising—nurseries in the making. They were large enough to hold their gases close, swaddling themselves in atmosphere, [and] small enough to stay solid, never swelling into gaseous giants. They were “Goldilocks planets,” our own astronomers would say: just right for life.

But one planet lived; the other, died. One turned green; the other, red. One has seven billion people on it; the other, none. Why are we so different?



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