Phoenix will enter the top of the Martian atmosphere at almost 21,000 km/h (almost 13,000 mph). In seven minutes, the spacecraft must complete a challenging sequence of events to slow to about 8 km/h (5 mph) before its three legs reach the ground. Confirmation of the landing could come as early as 23:53 UTC.

"This is not a trip to grandma's house. Putting a spacecraft safely on Mars is hard and risky," said Ed Weiler, associate administrator for NASA's Science Mission Directorate at NASA Headquarters in Washington. "Internationally, fewer than half the attempts have succeeded."

Rocks large enough to spoil the landing or prevent opening of the solar panels present the biggest known risk. However, images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, detailed enough to show individual rocks smaller than the lander, have helped lessen that risk.

"We have blanketed nearly the entire landing area with HiRISE images," said Ray Arvidson of Washington University in St. Louis, chairman of the Phoenix landing-site working group. "This is one of the least rocky areas on all of Mars and we are confident that rocks will not detrimentally impact the ability of Phoenix to land safely."

Phoenix uses hardware from a spacecraft built for a 2001 launch that was canceled in response to the loss of a similar Mars spacecraft during a 1999 landing attempt. Researchers who proposed the Phoenix mission in 2002 saw the unused spacecraft as a resource for pursuing a new science opportunity.

Earlier in 2002, NASA's Mars Odyssey orbiter discovered that plentiful water ice lies just beneath the surface throughout much of high-latitude Mars. NASA chose the Phoenix proposal over 24 other proposals to become the first endeavor in the Mars Scout program of competitively selected missions. "Phoenix will land farther north on Mars than any previous mission," said Phoenix Project Manager Barry Goldstein of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Credit: NASA/JPL-Caltech.
High resolution image (0.0 MB).

The landing site chosen for NASA's Mars Phoenix Lander, at about 68° north latitude, is much farther north than the sites where previous spacecraft have landed on Mars.

Color coding on this map indicates relative elevations based on data from the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor. Red is higher elevation; blue is lower elevation. In longitude, the map extends from 70° (north) to minus 70° (south).




Credit: NASA/JPL-Caltech/University of Arizona.

Bright green indicates areas with few large rocks on this shaded relief map of the area in and around the targeted landing site for NASA's Mars Phoenix Lander.

The rectangular patches color-coded with bright green, red and yellow are areas where rock abundance has been tabulated from images taken by the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter. The key is on the legend of the map. For example, each hectare (2.5 acres) of the green-coded areas has three or fewer rocks with a width of 1.5 meters (5 feet) or more. The red-coded areas have more then 19 rocks that size per hectare.




Credit: .

Researchers assessing the targeted landing area for NASA's Phoenix Mars Lander have used images from a powerful telescopic camera on NASA's Mars Reconnaissance Orbiter to count rocks in and around the intended landing area.

This image from the orbiter's High Resolution Imaging Science Experiment (HiRISE) camera shows ground with very few rocks, close the center of the landing target. It also shows patterned ground, fractured into polygons. Similar polygonal patterns can be found in some areas of repeated freezing and thawing on Earth. The relief of the polygons in this image is highlighted by a low sun angle.




Credit: NASA/JPL-Caltech/University of Arizona.

This image shows ground with a farily high abundance of rocks, west of the landing target. It also shows patterned ground, fractured into polygons. Similar polygonal patterns can be found in some areas of repeated freezing and thawing on Earth. The relief of the polygons in this image is highlighted by a low sun angle.

For scale, an illustration of the Phoenix lander, which is about 5.5 meters (18 feet) by 2 meters (7 feet), is artificially superimposed on a full-resolution subset of HiRISE image (right).




Credit: NASA/JPL-Caltech/University of Arizona.

This shaded relief map shows the topography and color-coded types of terrain in and around the targeted landing site for NASA's Mars Phoenix Lander.

An impact crater informally named "Heimdall" lies in the orange-coded area northeast of the targeted landing site. The crater is about 10 kilometers (6 miles) wide. Material ejected from Heimdall has been mapped as a rocky inner portion (orange) and an outer portion (yellow). The outer ejecta is relatively rock-free, as is the "lowland bright" unit (light blue), which is probably an even farther-out portion of where material ejected from Heimdall has been deposited. These two ejecta units thus provide a rock-free and flat terrain for the Phoenix landing.

The "lowland dark" (dark blue) unit has more rocks detectable from orbit than the lowland bright unit.

"The Phoenix mission not only studies the northern permafrost region, but takes the next step in Mars exploration by determining whether this region, which may encompass as much as 25 percent of the Martian surface, is habitable," said Peter Smith, Phoenix principal investigator at the University of Arizona, Tucson.

The solar-powered robotic lander will manipulate a 2.35 meter arm (7.7 foot) to scoop up samples of underground ice and soil lying above the ice. Onboard laboratory instruments will analyze the samples. Cameras and a Canadian-supplied weather station will supply other information about the site's environment.

One research goal is to assess whether conditions at the site ever have been favorable for microbial life. The composition and texture of soil above the ice could give clues to whether the ice ever melts in response to long-term climate cycles. Another important question is whether the scooped-up samples contain carbon-based chemicals that are potential building blocks and food for life.

The Phoenix mission is led by Smith, with project management at JPL. The development partnership is with Lockheed Martin, Denver. International contributions are from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; the Max Planck Institute, Germany; and the Finnish Meteorological Institute.

Source: Jet Propulsion Laboratory
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