The Mars mystique

"It went into the oven, and it came out differently as a function of how far [planets] were from the sun. The last 10 years has challenged that assumption and shown us that there are specific and fundamental differences among the terrestrial planets, even though [they are] really close together."

The geological processes that shape these planets "are fundamentally the same," she says. "But the way they play out in detail, which we can see with the exploration program we've had over the last 10 years, is very different."

It turns out, for instance, that Mars' crust has much higher levels of sulfur than Earth's crust. While the distinction might seem esoteric, it suggests a far different environment early in the planet's history than Earth's – one that would have a direct influence on any life that might have emerged then, Dr. Dyar says.

Efforts to follow the water have revealed a remarkable planet whose prospects for serving as a habitat – even if it ultimately didn't host life of any sort – seem to increase with each new mission.

From high above the planet, two orbiters – Mars Global Surveyor and Mars Odyssey (the first mission in a revamped NASA Mars exploration program following the 1999 debacles) – returned images of fans and flows of sediment from the earliest period of Martian history. The teams interpreting the images, published in 2003, concluded that the features represented evidence of long-lived flows of water moving across the surface.

At the same time, images from Mars Odyssey showed channels cut into the sides of craters and along other slopes, suggesting brief catastrophic releases of water in the geologically recent past.

A year later, after Opportunity landed, it found tiny spheres of minerals sprinkled across the surface and embedded in a layer of sediment that was part of a rocky outcropping the rover was examining. Researchers dubbed the spheres "blueberries," later identified as made of the mineral hematite, which form in water-saturated soil deposits. Last September, the team said it had discovered similar spheres in a formation at Endeavour Crater, but with different compositions. In addition, the rover has detected veins of gypsum and clays in the rocks, further suggesting water in the area early on.

Curiosity has added to the growing evidence. In its brief sojourn, the rover has already helped scientists identify rounded rocks, as well as rocks bound up in cemented clumps of soil, that point to the presence of an ancient riverbed etched on the floor of Gale Crater billions of years ago.

Comparing timelines for the geological evolutions of Earth and Mars, as well as for the emergence of life on Earth, "it becomes abundantly clear that, yes, there probably was persistent standing water on Mars long enough" for life to have evolved in the same fashion it did on Earth, Dyar says.

Now, Curiosity, with its ability to zap, drill, and analyze rock and soil, while rolling across the surface of Mars (and leaving JPL's initials in Morse code in its tracks), is taking the next step: hunting for potential ancient habitats. Yet even if it comes up dry, the mission holds the promise of writing a new chapter in humanity's Book of Mars, and perhaps even Book of Earth.

"I can't imagine being disappointed scientifically, even if we don't find carbon" or features that strongly indicate that the area was not only habitable, but in fact did support life, said John Grotzinger, the mission's lead scientist, during a prelanding briefing.

* * *

Curiosity's path up Gale Crater's Mt. Sharp is essentially a stroll through geological time and environmental history on Mars – one that represents a strong contrast to that on Earth, where life did evolve.

"Even in the case where life was never present on Mars, I still see [the mission] as an extraordinary opportunity to get a bearing on our own existence on Earth," Dr. Grotzinger said.

Previous

1 | 2 | 3 | 4 | 5

Next