Four finalist landing site candidates for Mars Science Laboratory
Wed Nov 19, 2008 at 22:03 UTC
Out of more than 30 sites considered as possible landing targets for NASA's Mars Science Laboratory mission, by November 2008 four of the most intriguing places on Mars rose to the final round of the site-selection process.
The four finalists are, alphabetically:
- Eberswalde - where an ancient river deposited a delta in a possible lake.
- Gale - with a mountain of stacked layers including clays and sulfates.
- Holden - a crater containing alluvial fans, flood deposits, possible lake beds and clay-rich deposits.
- Mawrth - which shows exposed layers containing at least two types of clay.
Credit: NASA/JPL-Caltech.
High resolution image
The locations of these four candidates are indicated here on a background map of color-coded topographical data from the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor. Red is higher elevation; blue is lower elevation. In latitude, the map extends from 70 degrees (north) to minus 70 degrees (south). The east-west axis is labeled at the top in degrees of east longitude, with the zero meridian at the center.
The Mars Science Laboratory mission's capabilities for landing more precisely and at higher elevation than ever before, for driving farther, and for generating electricity without reliance on sunshine have enabled consideration of a wider range of possible landing sites than for any previous Mars mission. During the past two years, multiple observations of dozens of candidate sites by NASA's Mars Reconnaissance Orbiter have augmented data from earlier orbiters for evaluating sites' scientific attractions and engineering risks.
More than 100 Mars scientists have participated in a series of open workshops presenting and assessing data that the orbiters have provided about the candidate sites. The four sites rated highest by researchers at a September 2008 workshop were the same ones chosen by mission leaders after a subsequent round of safety evaluations and analysis of terrain for rover driving.
As a clay-bearing site where a river once flowed into a lake, Eberswalde Crater offers a chance to use knowledge that oil industry geologists have accumulated about locations of the most promising parts of a delta to look for any concentrations of carbon chemistry that is crucial to life.
The mountain inside Gale Crater could provide a route for the rover to drive up a 5-kilometer (3-mile) sequence of layers, studying a transition from environments that produced clay deposits near the bottom to later environments that produced sulfate deposits partway up.
Running water once carved gullies and deposited sediments as alluvial fans and catastrophic flood deposits in Holden Crater, a site that may also present the chance to evaluate layers deposited in a lake. Exploration of key features within this target area would require drives to the edge of a broad valley, and then down into the valley.
Mawrth Valley is an apparent flood channel near the edge of vast Martian highlands. It holds different types of clays in clearly layered context, offering an opportunity for studying the changes in wet conditions that produced or altered the clays. The clay signatures are stronger than at the other sites, and this is the only one of the four for which the science target is within the landing area, not nearby.
Credit: NASA/JPL-Caltech.
Eberswalde Crater offers the chance to explore an ancient river delta. In fact, the delta is the most convincing sign that a Martian river once flowed into a standing body of water. Stream channels in the delta have meandered over time. As the streams carved new channels, abandoned streambeds remained behind as "footprints." Today, many of these streambeds are higher than the surrounding terrain. That's because the water deposited sediments that hardened and became resistant to erosion. Orbiters above Mars have detected clay minerals in the sediments. Clays are evidence of past water activity for the Mars Science Laboratory to investigate. Clays form when water dissolves rocks into extremely fine-grained minerals. These minerals form layers, kind of like the parts of a sandwich.
Credit: NASA/JPL-Caltech.
Gale Crater is a fascinating place to explore because of the mountain of layered materials in the middle. On Earth, this mound would be a mountain 5 kilometers (3 miles) high! The layers tell a story about what Mars was like in the past, perhaps spanning much of the history of the red planet. Studies from orbit have revealed that the layers have different minerals depending on their height. Near the bottom of the mound are clay minerals. Above the clay-bearing layers are layers with sulfur and oxygen-bearing minerals are above them. Flowing water appears to have carved channels in both the mound and the crater wall. To get to the mound, the Mars Science Laboratory would land in a flatter part of the crater and carefully work its way upward, layer by layer. Along the way, the rover would investigate how the layers formed and the environments in which they formed.
Credit: NASA/JPL-Caltech.
Holden Crater sits within a string of craters that look like a chain of alpine lakes connected by a stream. The crater offers tantalizing clues to the history of water on Mars. Running water carved deep gullies in the crater. Water also carried sediments onto the floor of a prospective lakebed. These deposits are more than 3 billion years old, dating back to a wetter period of early Martian history. Geological studies suggest that a massive, catastrophic flood may have breached part of the crater rim that was holding back water. The water eventually disappeared. Later, wind eroded the surface and exposed ancient sediments. Winds also formed ripples and dunes that are still visible on the surface today. Holden Crater offers the opportunity to examine some of the most ancient rocks on Mars. Another benefit of the site is that the mission would not have to drive far to get there. The rover would land on top of a "bajada," a high plateau of material eroded from nearby cliffs.
Credit: NASA/JPL-Caltech.
Mawrth Vallis is smack in the middle of a region that has always been mysterious to scientists. This region is the boundary between the southern highlands and northern lowlands of Mars. It is a place where the entire planet suddenly drops in elevation. In effect, Mars is lopsided. Its southern hemisphere is higher in elevation than its northern hemisphere. Mawrth Vallis itself is an ancient channel carved by catastrophic floods. "Mawrth" is the Welsh word for Mars and "Vallis" is Latin for valley. Layered cliffs, which look like Neapolitan ice cream, are rich in clay minerals. Such minerals, called phyllosilicates, form in the presence of water. They may yield information about past environments that could have supported life. Mawrth Vallis is also conveniently near a hazard-free landing zone. The Mars Science Laboratory science team would use the rover to piece together the history of this puzzling site and look for conditions favorable to life.
| Source: Jet Propulsion Laboratory | |
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