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  sci-tech > space > story pagecorner  

Latest images from Mars show details of layers, craters

Deposits
Southern layered deposits  

November 23, 1999
Web posted at: 3:55 p.m. EST (2055 GMT)

By Amanda Barnett
CNN Interactive Staff Writer


In this story:

Layers at the south pole

Craters within craters

Antarctic-style polygons

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(CNN) -- Some of the latest images taken by the Mars Global Surveyor, which has been mapping the red planet since earlier this year, reveal just how much work is ahead for the Mars Polar Lander, scientists said Tuesday.

"Even with this preview people are still quite perplexed," said Ken Edgett a scientist with Malin Space Science Systems, the company that's controlling the camera on the Global Surveyor. "It's such a different type of terrain. It's definitely going to be different from the other places we've landed before."

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The Global Surveyor's camera has sent back new pictures of layered deposits at the planet's south pole, the area that will be explored from the ground by the Polar Lander.

Global Surveyor also has sent back detailed pictures of a crater three times larger than Arizona's famous Meteor Crater and polygon patterns in Mars' southern hemisphere.

Layers at the south pole

Edgett says that Global Surveyor sends back hundreds of pictures each week, but scientists have been training its cameras on the south pole to prepare for the Polar Lander's December 3 arrival.

Both polar regions on the planet are blanketed by thick accumulations of layered material. Polar Lander will touch down on the upper surface of one of those layered areas known as the "South Polar Layered Deposits" to search for water.

A new picture from the Global Surveyor shows one of the clearest and highest-resolution images ever obtained of the area. The picture covers an area approximately 340 miles (550 km) northwest of where the Polar Lander will set down.

The picture cover an area almost a mile (1.5 km) wide and two miles (4.6 km) long. The smallest objects that can be seen are about the sizes of automobiles. Small dark streaks in the upper right of the photo are formed by winds that have blown small patches of sediment across the surface of the layered material.

"There are many more layers in these deposits than anyone thought ... and they're thinner," Edgett said.

Based on data from the Mariner and Viking projects in the 1970s, the polar layered deposits have long been considered to hold accumulations of dust and ice. The layering may hold clues about climate change on Mars. An earthbound analogy would be tree rings -- periods of drought and rain affect the width of the rings.

Craters within craters

Craters
Detail of a crater in the Nepenthes Mensae region of Mars  

Craters are one of the few landforms that Mars shares in common with the other planets and moons of our solar system.

The Global Surveyor gave scientists a close-up view of a 1.9 mile (3 km) wide impact crater on the floor of a larger crater in the Nepenthes Mensae region of Mars.

The smaller crater is three times wider than the famous Meteor Crater in northern Arizona.

The high resolution image shows many small windblown drifts or dunes in the low areas both within the crater and outside on the surrounding terrain.

Some portions of the crater's walls have outcrops of bare, layered rock. Large boulders have been dislodged from the walls and have tumbled down the slopes to the crater floor. Many of these boulders are bigger than school buses and automobiles.

Antarctic-style polygons

Polygons
These polygon formations in Mars' southern polar region resemble those that form in Earth's arctic regions.  

One photo, taken in October, shows a relatively smooth Martian "plain" covered with polygons like those commonly found at Earth's arctic and antarctic regions. Polygons form when the ground freezes and thaws repeatedly over the course of time.

The polygons were photographed at Malea Planum in the far southern regions of Mars. Patches of frost from the retreating south polar ice cap are caught in the cracks making them more visible.

"These are key indicators of ice in the ground near the surface," Edgett said.

Scientists say finding polygons at the Malea Planum indicates that ice is not too deeply buried because only a thin veneer of material appears to have covered the crater at the top of the scene.

The $150 million Mars Global Surveyor mission was launched in 1996 and arrived at Mars the following year. It has orbited the red planet for a full Martian year, or 26 months. It started collecting extensive data earlier this year.



RELATED STORIES:
NASA: Human error caused loss of Mars orbiter
November 10, 1999
Surface hazards force NASA to rethink Mars landing site
October 22, 1999
Course of Mars Lander corrected for December landing
October 30, 1999
NASA decides to stick with original Mars landing site
October 26, 1999
Destination Mars


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Mars Global Surveyor
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