New questions arise about Mars; future probes are in doubt
Newhouse News Service
Just as the lure of Mars grows stronger, with scientists poring over tantalizing new evidence of an ancient ocean and fresh views of layered canyons, sculpted polar ice caps and swirling dust devils, missions to the Red Planet are in disarray.
The back-to-back failures of the Mars Polar Lander and Mars Climate Orbiter late last year have NASA rethinking what kind of spacecraft it will send to the planet most like our own.
Investigators studying what ought to be done with future Mars probes are to report their findings this month. Substantial retooling is expected as the space agency and its critics debate whether NASA's philosophy of undertaking more small-scale, cheap, quick missions has been stretched too far.
But more questions arise
Meanwhile, a satellite orbiting Mars is relaying stunning photos and laser scans of the planet's dusty red, surprisingly varied surface. The rich data have scientists itching for the greater detail that additional missions or even manned landings could provide.
Public enthusiasm for such efforts may ratchet up with an onslaught of Mars-themed movies. Brian DePalma's "Mission to Mars" is out this month, while "Red Planet," starring Val Kilmer, debuts this summer. And "Titanic" director James Cameron is shooting a Mars TV miniseries and an IMAX film.
But the Hollywood images will be hard-pressed to match what the plucky Mars Global Surveyor has been beaming back to Earth since it began mapping a year ago. The wealth of information is changing the concept of the planet that scientists had held since the Viking 1 and 2 missions in the mid-1970s.
"The Mars we thought we knew for 25 years was not there," said Ken Edgett, a scientist with Malin Space Science Systems, the company that operates Global Surveyor's cameras for NASA. "It's a history previously unperceived."
That history is etched in the dark layers the orbiter documented on the steep walls of the Valles Marineris, a vast gorge system near Mars' equator almost 500 times bigger than the Grand Canyon.
Each layer is a record of what was happening on Mars' surface during a period of time, capturing "God only knows what stories," Edgett said. Scientists think some of the layers could date to very early in Mars' 4.5 billion years.
Extinct volcanoes triple the height of Mount Everest loom on the horizon. Tornadic dust devils whirl crazily across the surface; last month, Global Surveyor's cameras for the first time caught the whirlwinds carving veiny tracks previously seen in the Martian sand.
Global Surveyor is providing data that deepens the debate about whether oceans covered those sands. The presence of water would increase chances that living things, however microscopic, might have eked out a foothold on ancient Mars.
There are surface remnants of huge natural channels and branching valleys that look like drainage paths water has cut on Earth. (These aren't the supposedly alien-dug Martian canals of astronomy lore that turned out to be optical illusions.)
A 3-D map
For months, a laser aboard Global Surveyor bounced pulses of light off Mars' surface in millions of locations. The measurements produced the first 3-D topographic map of the entire planet.
The map shows evidence of a possible ancient ocean in the planet's table-flat northern lowlands, according to a team of Brown University scientists.
The clues include a nearly level border that may have been a shoreline, with stair-stepped terraces parallel to it that waves may have gouged as the Martian sea receded.
"We can't think of anything else (besides big lakes or oceans) to explain these things," said Brown planetary geologist James Head.
The only way to know for certain is to return with more advanced survey missions and, ultimately, to bring Mars samples back to Earth.
Next up is Mars Surveyor Orbiter, due to lift off in spring 2001 to map the mineral makeup of the planet's surface. Its design is unlikely to change, considering the dwindling time until launch.
Some changes might be possible, however, to Mars Surveyor Lander, a more complex craft. It is supposed to carry experiments testing the suitability of Mars' environment for future human landings, as well as a camera- and sampler-equipped rover.
The most ambitious, complex and tenuous flight planned is the Mars Sample Return mission. Beginning in 2003, robotic landers and rovers will journey to Mars, scoop up rock and soil samples, and launch them into orbit, where a waiting French craft will snag the canisters and whisk them back to Earth by 2008.
NASA's retooling probably won't change the overall intent of those missions but may slow the pace, said Cornell University's Steven Squyres, involved in Mars planning. "All constraints have been taken off except to do great science and don't bust the budget. I think you may see a plan that has the same goals but a different timetable."
Ultimately, though, if Mars' new mysteries are to be solved, humans will have to set foot on the Red Planet. As Edgett says, "We're seeing a Mars you're not going to understand unless you go there."
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