Robots Hammer Red Planet
Ed. note: First rover scheduled to launch June 10, 2003. (The June 8/9 launches were scrubbed due to weather conditions.)
On Sunday, June 8th, NASA’s Mars Exploration Rover (MER) project kicks off by launching the first of two unique robotic geologists. The identical rolling rovers see sharper images, can explore farther and examine rocks better than anything that’s ever landed on Mars. Each rover can explore up to half a kilometer (just under one-third of a mile) away from their respective touchdown locations.
|Delta launch rocket for MER mission.|
Both rover missions will lift off from Cape Canaveral Air Force Station, Fla., on Delta II launch vehicles. Launch opportunities begin for the first mission at 2:06 p.m. (EDT) June 8 and for the second mission at 12:38 a.m. (EDT) June 25, and repeat twice daily, for up to 21 days, for each mission.
The first MER will arrive at Mars on Jan. 4, 2004, the second, Jan. 25. Plans call for each to operate for at least three months.
"The instrumentation onboard these rovers, combined with their great mobility, will offer a totally new view of Mars, including a microscopic view inside rocks for the first time," said Dr. Ed Weiler, associate administrator for space science, NASA Headquarters, Washington. "However, missions to Mars have proven to be far more hazardous than missions to other planets. Historically, two out of three missions, from all countries who have tried to land on Mars, ended in failure. We have done everything we can to ensure our rovers have the best chance of success," Weiler said.
|Artist conception of dramatic airbag landing Credit: NASA.|
Preparing a robot to perform to exact specifications on a harsh planet 460 million kilometers (286 million miles) away is no easy task.
These missions continue NASA’s quest to understand the role of water on Mars. "We will be using the rovers to find rocks and soils that could hold clues about wet environments of Mars’ past," said Dr. Cathy Weitz, MER Rover program scientist at NASA Headquarters. "We’ll analyze the clues to assess whether those environments may have been conducive to life."
First, the rovers have to safely reach Mars. "The rovers will use innovations to aid in safe landings, but risks remain," said Peter Theisinger, MER project manager at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif.
In particular, the aero-shell that protects the rovers will slam into the Martian atmosphere at 14,000 miles per hour, then deploy an approximately 12 minute sequence of parachutes opening, followed by airbag inflation. As the capsules hit the surface and bounce to their resting places, these airbags that surround the landers will cushion the blow. The new rovers could bounce as far as 0.6 miles in the course of their settling phase. The rovers will bounce to airbag-cushioned landings at sites offering a balance of favorable conditions for safe landings and interesting science.
Gusev Crater: January 4, 2004
|"If something like Ma’adim Vallis (above) is actually a lava flow and looks so much like a fluvial channel, well, we better reassess what we think about the channels we’re seeing on Mars." -Nathalie Cabrol|
Credit: R. Irwin III (CEPS/NASM,UVa), T. Maxwell, A. Howard, R. Craddock, D. Leverington
The designated site for the first mission is Gusev Crater. Gusev is a large crater basin, some 170 kilometers (105 miles) across. Most scientists believe it once was fed by water flowing through an enormous valley channel, Ma’adim Vallis. Snaking its way northward along the Martian landscape for more than 900 kilometers (560 miles), Ma’adim Vallis is 1.5 times as long as the Grand Canyon.
In images of Gusev taken by the Mars Orbital Camera (MOC) aboard the orbiting Mars Global Surveyor (MGS) spacecraft, some exposed outcrops appear to show faint layering. The prevailing scientific theory is that Gusev Crater contains sediment washed down Ma’adim Vallis from the highlands to the south nearly 4 billion years ago.
Some researchers also believe that landforms visible in MOC images of the mouth of Ma’adim Vallis, where it enters Gusev Crater, resemble landforms seen in some terrestrial river deltas.
"Deltas of this nature take tens of thousands of years, hundreds of thousands of years on Earth to be formed," says Nathalie Cabrol of the SETI Institute and NASA Ames Research Center. "So here you have the place where water has been acting for a long time. And depositing and eroding sediments and shaping the landscape for – possibly that long."
Meridiani Planum: January 25, 2004
|(Click to view details) Terra Meridiani, hematite-rich and a probable test for the Mars’ wet hypothesis|
Credit: Malin Space Systems/ARC/JPL/NASA
The second rover will go to a site called Meridiani Planum. On contemporary maps of Mars, Meridiani Planum is in dead center. What makes it an exciting spot is that it is the site of a vast deposit of gray hematite. According to Phil Christensen, of Arizona State University, there are five possible scenarios for how the hematite in Meridiani Planum formed: four of these involve liquid water; the fifth is a volcanic process that Christensen considers unlikely. Christensen explains the various possibilities this way: "If you get there and you picked up a rock and it had some banding layers of hematite in it, that’s a smoking gun for a lake deposit.
"Gusev and Meridiani give us two different types of evidence about liquid water in Mars’ history," said Dr. Joy Crisp, MER project scientist at JPL. "Gusev appears to have been a crater lake. The channel of an ancient riverbed indicates water flowed right into it. Meridiani has a large deposit of gray hematite, a mineral that usually forms in a wet environment," Crisp said.
Gusev Crater is almost exactly halfway around the red planet from Meridiani Planum.
Robotic Field Geologists
|A simulated image of the new Mars rover carrying the Athena science instruments.|
The rovers, working as robotic field geologists, will examine the sites for clues about what happened there. "The clues are in the rocks, but you can’t go to every rock, so you split the job into two pieces," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the package of science instruments –called Athena–on the rovers.
To complete their scientific deployment, the rovers and landers must go through 17 carefully-orchestrated steps — from rolling out exit ramps for the rovers, to unfolding the solar arrays and popping the camera masts up — just so the rover can venture out and explore the red soil.
First, a panoramic camera at human-eye height, and a miniature thermal emission spectrometer, with infrared vision, help scientists identify the most interesting rocks. The rovers can watch for hazards and maneuver around them. Each six-wheeled robot has a deck of solar panels, about the size of a kitchen table, for power. The rover drives to the selected rock and extends an arm with tools on the end. Then, a microscopic imager, like a geologist’s hand lens, gives a close-up view of the rock’s texture. Two spectrometers identify the composition of the rock. The fourth tool substitutes for a geologist’s hammer. It exposes the fresh interior of a rock by scraping away the weathered surface layer.
"We see the twin rovers as stepping stones for the rest of the decade and to a future decade of Mars exploration that will ultimately provide the knowledge necessary for human exploration," said Orlando Figueroa, director of the Mars Exploration Program at NASA Headquarters.