January 24, 2004

NASA’s Opportunity Rover Lands on Mars Tonight

On January 24, 2004, NASA's Mars rover Opportunity is scheduled to land on a Martian plain in search of evidence for water.

[email protected] -- On January 24, at about 9:05 p.m. Pacific Standard Time, NASA's second rover is scheduled to arrive on Mars.

Opportunity will land near the equator, on a plain known as Meridiani Planum. It'll be halfway around the planet from Gusev Crater, where its twin, Spirit, is already feeding eager scientists as much data as it can transmit.

Meridiani Planum interests scientists because it contains an ancient layer of hematite, an iron oxide that, on Earth, almost always forms in an environment containing liquid water.

The site appears dry now. So how did the hematite get there? Was there once water in the area? If so, where did it go?

"There are five or six hypotheses to explain the hematite on Mars, but none of them are a slam-dunk," says NASA's Mars Landing Site Science Coordinator John Grant. "We have to go there to find out which is correct."

It's possible, for example, that the hematite was produced directly from iron-rich lavas, a process that would not require liquid water. But if water was involved -- and that's considered most probable -- then, most likely, the hematite either formed from the iron-rich waters of an ancient lake, or it formed when Martian groundwater percolated though layers of volcanic ash.

Opportunity's suite of spectrometers, cameras, microscopes, and sampling tools should allow scientists to figure out where the hematite came from.

For instance, if a mineral called goethite is found among the hematite, that would mean that the hematite formed in watery conditions. On the other hand, if magnetite is found and goethite is not, a watery past is unlikely.

Just being able to look at the way the hematite is distributed will provide some answers. If the hematite occurs as a thin layer within a pile of layers, then it's likely to have formed in a long-ago lake, says Grant.

If, on the other hand, it occurs in more discrete veins, deposited between cracks in rocks, "then it's much more likely to have been associated with groundwater."

If you look in the Earth, he says, in places where the groundwater percolates through the subsurface, "you see evidence for life all over the place." This mission, Grant emphasizes, is not seeking evidence of Martian life. It's looking for environments that were favorable for life, and in which evidence of life may have been preserved.

Knowing how the hematite formed will help determine if Meridiani Planum is that kind of environment.

Meridiani Planum is unique on Mars because there's so much exposed hematite there, according to data gathered by NASA's Mars Global Surveyor spacecraft.

"Localized deposits also exist in two other sites: the deep canyon Valles Marinaris and a place called called Aram Chaos," notes Grant, "but neither are accessible based on the current landing system." Meridiani Planum has more hematite and it's a safer place to land.

Meridiani Planum is also attractive because the site appears to be eroding, with once-buried craters that are now half-revealed. Opportunity might be able to inspect layers of ground that would otherwise be hidden, affording a glimpse into the area's distant past.

"There's so much we don't know about Mars," says Grant. "But I really think we're going to come out of this mission with a better understanding of what Mars has been like over time, and where we might go for our next step."

About the Mars Exploration Rover Mission

NASA's twin robot geologists, the Mars Exploration Rovers, launched toward Mars on June 10 and July 7, 2003, in search of answers about the history of water on Mars. Spirit landed on January 3, and Opportunity is scheduled to land on January 24, 2004.

The Mars Exploration Rover mission is part of NASA's Mars Exploration Program, a long-term effort of robotic exploration of the red planet.

Primary among the mission's scientific goals is to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. The spacecraft are targeted to sites on opposite sides of Mars that appear to have been affected by liquid water in the past.

The landing sites are at Gusev Crater, a possible former lake in a giant impact crater, and Meridiani Planum, where mineral deposits (hematite) suggest Mars had a wet past.

After the airbag-protected landing craft settle onto the surface and open, the rovers will roll out to take panoramic images.

These will give scientists the information they need to select promising geological targets that will tell part of the story of water in Mars' past. Then, the rovers will drive to those locations to perform on-site scientific investigations over the course of their 90-day mission.

These are the primary science instruments to be carried by the rovers:

-- Panoramic Camera (Pancam): for determining the mineralogy, texture, and structure of the local terrain.

-- Miniature Thermal Emission Spectrometer (Mini-TES): for identifying promising rocks and soils for closer examination and for determining the processes that formed Martian rocks. The instrument will also look skyward to provide temperature profiles of the Martian atmosphere.

-- Mössbauer Spectrometer (MB): for close-up investigations of the mineralogy of iron-bearing rocks and soils.

-- Alpha Particle X-Ray Spectrometer (APXS): for close-up analysis of the abundances of elements that make up rocks and soils.

-- Magnets: for collecting magnetic dust particles. The Mössbauer Spectrometer and the Alpha Particle X-ray Spectrometer will analyze the particles collected and help determine the ratio of magnetic particles to non-magnetic particles. They will also analyze the composition of magnetic minerals in airborne dust and rocks that have been ground by the Rock Abrasion Tool.

-- Microscopic Imager (MI): for obtaining close-up, high-resolution images of rocks and soils.

-- Rock Abrasion Tool (RAT): for removing dusty and weathered rock surfaces and exposing fresh material for examination by instruments onboard.

A goal for the rover is to drive up to 40 meters (about 44 yards) in a single day, for a total of up to one 1 kilometer (about three-quarters of a mile).

Moving from place to place, the rovers will perform on-site geological investigations. Each rover is sort of the mechanical equivalent of a geologist walking the surface of Mars. The mast-mounted cameras are mounted 1.5 meters(5 feet) high and will provide 360-degree, stereoscopic, humanlike views of the terrain.

The robotic arm will be capable of movement in much the same way as a human arm with an elbow and wrist, and will place instruments directly up against rock and soil targets of interest.

In the mechanical "fist" of the arm is a microscopic camera that will serve the same purpose as a geologist's handheld magnifying lens. The Rock Abrasion Tool serves the purpose of a geologist's rock hammer to expose the insides of rocks.


Author: Karen Miller

The Science Directorate at NASA's Marshall Space Flight Center sponsors the [email protected] web sites. The mission of [email protected] is to help the public understand how exciting NASA research is and to help NASA scientists fulfill their outreach responsibilities.


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