Next Tuesday, NASA will celebrate the first anniversary of the successful landing of its Mars Exploration Rover A, better known as Spirit. That craft, which parachuted through the Martian atmosphere and then bounced via airbags to a stop in a large equatorial expanse called Gusev crater, is still operating after more than tripling its expected lifetime of 90 Martian days, or sols.

Later next month, Opportunity, Spirit's twin and known formally as Mars Exploration Rover B -- which landed Jan. 24 -- likewise should reach its first anniversary. The rover also landed on the Martian equator in an area called Meridiani Planum. It has identified several types of minerals that only form in the presence of liquid water.

Opportunity is in even better shape than Spirit, according to mission specialists at NASA's Jet Propulsion Laboratory in Pasadena, Calif. The solar-powered craft continues to maintain 90 percent of its original electrical output and, aside from a few minor glitches, is performing normally.

All in all, the two golf-cart-size rovers have accomplished exactly what their designers had hoped: They have uncovered highly persuasive evidence that water once flowed on the surface of Mars -- even to the point of creating sediments and wave action over a long-enough timeframe to sculpt the texture of rocks.

Not that any of this was unexpected. Surveys of the red planet by NASA's Mars Global Surveyor and Odyssey orbiters, and the European Space Agency's Mar Express spacecraft, have captured detailed images of the Martian surface showing features that closely resemble gullies and stream channels on Earth.

That evidence was circumstantial, however. Scientists needed to see mineral analysis that showed the action of water on rock. That is what Opportunity and, to a lesser degree, Spirit, have reported. So, the difference between now and this time last year is the existence of hard chemical data demonstrating there once was another planet in the universe where water once flowed.

The onetime presence of liquid water on Mars begs one big and a second, even bigger, question:

--Did the red planet ever host life?

--Did that life spring up independently?

The answer to the first could come within 10 years, when the next NASA lander bound for Mars -- the Volkswagon-sized, radioisotope-powered Mars Science Laboratory -- touches down in the fall of 2010 and spends perhaps several years roaming the surface, examining soil samples and, possibly, discovering fossils or even living organisms.

There is even a tantalizing suggestion that life on Mars is indeed active. The Mars Express orbiter, which has been operating since Christmas day 2003, discovered the presence of methane in the planet's atmosphere, confirming previous ground-based observations.

Methane is a strong indicator of life because it is the product of microbial action and it has a short lifetime in the atmosphere because sunlight breaks it down. If something is producing methane, something is alive. The other possibility is, like on Earth, there is some vast underground reservoir of the gas left over from a bygone age -- but that age would have had to be alive.

The second, bigger, question is a subtle matter, whose full resolution will have to wait a long time, perhaps decades, when a round-trip probe snags a Martian organism and returns it to Earth for DNA analysis. Or, perhaps, its resolution will require decades more, until humans land on Mars and conduct the analysis onsite.

If Martian organisms, living or fossilized, are discovered, the full weight of that discovery cannot be known until their origin is established. If it turns out they are directly related to life on Earth, then it simply means life on the two planets shared a common source.

If, on the other hand, life is found on Mars that had a different origin than life on Earth, then it would be a most humbling experience, a -- to use a phrase coined by British cultural historian James Burke -- day the universe changed. Life would have sprung up independently on two different worlds, meaning it could just as easily have sprung up on hundreds, thousands, millions or billions of other planets throughout the cosmos.

Spirit, Opportunity and the other three robotic spacecraft currently operating on or around the red planet -- Mars Express, Mars Global Surveyor and Mars Odyssey -- have built a compelling case that the answer to an enormous question might lie as close as our planetary next-door neighbor.

Meanwhile, two other spacebound robots have begun contributing their own dazzling discoveries.

NASA's Cassini spacecraft since last July 4 has been orbiting Saturn and its moons in the first phase of a mission scheduled to last at least four years. Already it has transmitted images of stunning beauty as well as surprising data.

The Saturnian planetary system is exquisitely complex, with its spectacular rings and 33 moons -- the latter two of which Cassini discovered just a few days ago -- including Titan, the only moon in the solar system known to have an atmosphere. The spacecraft has revealed the gas giant has a previously undiscovered radiation belt, that its ring structure contains flowing waves -- probably caused by the gravitational action of its small shepherd moons -- and one of the components of those rings is something akin to mud.

Next month, the Huygens probe -- which is operated jointly by the ESA and the Italian Space Agency -- will make an unprecedented attempt to land softly on Titan's surface. Huygens, which separated successfully from Cassini on Christmas day, currently is on an unpowered trajectory to rendezvous with Titan. On Jan. 14, it is supposed to transmit images and data both all the way down and for a brief period on the surface, until Cassini -- which Huygens will use to relay its signals -- passes beyond the landing site and is blocked by the moon's mass from receiving.

Cassini and Huygens, like the twin Mars rovers, represent perhaps the most sophisticated robotic craft built so far. They are designed to act largely independently because the rovers -- and the Saturn craft even more so -- are beyond the range of direct control from mission scientists. For the past year, at JPL, scientists generally have been programming Spirit and Opportunity once a day, then waiting for the rovers to send back acknowledgments and new data. Round-trip signal travel time to the rovers is about 10 minutes, which prevents real-time instruction.

The situation is much more so for Cassini and Huygens, which currently are about 800 million miles away from Earth. A round-trip signal to the two craft takes more than 2 1/2 hours.

Despite these limitations, the rovers and the spacecraft have thus far performed spectacularly, advancing knowledge of the worlds they are visiting more in a matter of months than had been learned previously in all of human history. For this reason, 2004 in space could be called the triumph of the robots.

All rights reserved. � 2004 United Press International. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by United Press International. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of United Press International.

Related Links
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only