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Landing site: Challenger Memorial Station
Opportunity landed in Meridiani Planum at 354.47°E 1.95°S, about 24 km downrange (east) of her intended target. Although Meridiani is a flat plain, without the rockfields seen at previous Mars landing sites, Opportunity rolled into a small crater approximately 20 meters in diameter and it would be two weeks before she stuck a camera up to get a better look of her surroundings.
On 2004 January 28, NASA announced that the landing site was being named in honor of the seven astronauts of the final mission of space shuttle "Challenger, killed 18 years ago this day when the shuttle exploded shortly after launch.
Events and discoveries
First panorama
This 360-degree panorama is the first panorama beamed back to Earth from the Mars Exploration Rover Opportunity shortly after she touched down at Meridiani Planum, Mars. The image was captured by the rover's navigation camera.
First color panorama
This color image shows the martian landscape at Meridiani Planum, where the Mars Exploration Rover Opportunity successfully landed at 9:05 p.m. PST on January 24,2004. This is one of the first images beamed back to Earth from the rover shortly after she touched down. The image was captured by the rover's panoramic camera.
Opportunity lands in a crater
The interior of a crater surrounding the Opportunity at Meridiani Planum on Mars can be seen in this color image from the rover's panoramic camera. This is the darkest landing site ever visited by a spacecraft on mars. The rim of the crater is approximately 10 meters (32 feet) from the rover. The crater is estimated to be 20 meters (65 feet) in diameter. Scientists are intrigued by the abundance of rock outcrops dispersed throughout the crater, as well as the crater's soil, which appears to be a mixture of coarse gray grains and fine reddish grains. NASA Scientists were so excited about landing in a crater that they called this a "hole in one
Geologists said that the layers -- some no thicker than a finger -- indicate the rocks likely originated either from sediments carried by water or wind, or from falling volcanic ash. "We should be able to distinguish between those two hypotheses," said Dr. Andrew Knoll of Harvard University, Cambridge, a member of the science team for Opportunity and her twin, Spirit. If the rocks are sedimentary, water is a more likely source than wind, he said.
On Sol15, Opportunity took a close up of the rock Stone Mountain in the outcrop area of the crater.
From this picture it was speculated, that it does consist of very fine grain or dust. This is in contrast to Sandstone on Earth, which is compacted sand with rather large grains. Also, the weathering agent eroding away layers of this rock seems to be visible (dark spots).
"Embedded in it like blueberries in a muffin are these little spherical grains," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the rovers' scientific instruments. He also said: "One other teasure, a clue that just popped up, not gonna quote any numbers yet, but we have now completed an APXS measurement on the outcrop and it has got a lot of sulfur in it. Maybe a few times more sulfur than we've seen on any other location on Mars."
"Opportunity Ledge" outcroppings
This sweeping look at the unusual rock outcropping near Opportunity was captured by the rover's panoramic camera. Scientists believe the seemingly layered rocks are either volcanic ash deposits or sediments laid down by wind or water. It was given the name Opportunity Ledge.
A picture received on February 10 (and taken on Sol 16) had mission scientists excited. It showed that the thin layers in the bedrock are not always parallel. Instead, if you look closely at this image from an angle, you will notice that the lines converge and diverge at low angles. These unparallel lines give unparalleled clues that some "moving current" such as volcanic flow, wind, or water formed these rocks.
These layers with converging and diverging lines were a significant discovery for scientists who planned this mission to rigorously test the water hypothesis.
On February 19 the survey of Opportunity Ledge was declared successful. "We've planned our assault on the outcrop," said Dr. Squyres. A specific target in the outcrop (dubbed El Capitan) was selected for further investigation. "The whole stack of rocks seems to be well exposed here," he said of the chosen target. Upper and lower portions appear to differ in layering and weathering characteristics.
Opportunity reached El Capitan on Sol 27, and took first picture of the rocks with her Panoramic camera.
The image to the left shows a close up view of the layering in one section of this rock. El Capitan was named after a mountain in Texas, but on Mars, it is about 10 centimeters (4 inches) high. The upper and lower portions of El Capitan have different textures, and it was hoped that both areas could provide distinct and unique clues about the history of Mars.
Hematite
Geologists were eager to reach a hematite-rich area (in the center of the picture below) to closely examine the soil, which may reveal secrets about how the hematite got to this location. Knowing how the hematite on Mars was formed may help scientists characterize the past environment and determine whether that environment provided favorable conditions for life.
"Grey hematite is a mineral indicator of past water," said Dr. Joy Crisp, JPL project scientist. "It is not always associated with water, but it often is."
Scientists have wanted to find out which of these processes created grey hematite on Mars since 1998, when Mars Global Surveyor spotted large concentrations of the mineral near the planet's equator (seen in the left picture). This discovery provided the first mineral evidence that Mars' history may have included water.
"We want to know if the grains of hematite appear to be rounded and cemented together by the action of liquid water or if they're crystals that grew from a volcanic melt," said Crisp. "Is the hematite in layers, which would suggest that it was laid down by water, or in veins in the rock, which would be more characteristic of water having flowed through the rocks."
The next picture shows a mineral map, the first ever made on the surface of another planet, that was generated from a section of the panorama picture overlayed with data taken from the rover's Mini-TES. The Mini-TES spectral data was analyzed in a way that the concentration of the mineral hematite was deduced and its level coded in color. Red and orange mean high concentration, green and blue low concentration.
The next picture shows a hematite abundance "index map" that helps geologists choose hematite-rich locations to visit around Opportunitys landing site. Blue dots equal areas low in hematite and red dots equal areas high in hematite. The colored dots represent data collected by the miniature thermal emission spectrometer on Sol 11, after Opportunity had rolled off of the lander and the rover was located at the center of the blue semi-circle. (The spectrometer is located on the panoramic camera mast.)
The area to the left (with high concentration of hematite) was selected by mission members for further investigation, and called Hematite Slope.
During Sol 23 (February 16) Opportunity successfully trenched the soil at Hematite Slope and started to investigate the details of the layering.
Spherical Granules (Spherules)
Microscopic images of the soil taken by Opportunity revealed small, spherically shaped granules. They were first seen on pictures taken on Sol 10, right after the rover drove from the lander onto martian soil. The shapes by themselves don't reveal the particles' origin with certainty. "A number of straightforward geological processes can yield round shapes," said Dr. Hap McSween, a rover science team member from the University of Tennessee, Knoxville. They include accretion under water, but apparent pores in the particles make alternative possibilities of meteor impacts or volcanic eruptions more likely origins, he said.
For example, ranging in size from less than 100 microns to more than 250 microns, similar spherules were found in Moon soil samples collected by Apollo 12 at the Procellarum Basin, and Apollo 14 near Mare Imbrium (Sea of Rains), the dark crater that dominates the moon's face (1), and their properties were consistent with expectations for creation by meteor impacts (2).
In this picture, you can see them spread over the (smaller) soil grains. "We see these strange round objects we're calling "spherules" embedded in the outcrop, like blueberries in a muffin. The outcrop erodes away as it gets sandblasted, and the spherules (which seem to resist erosion better than the rest of the outcrop does) fall out and roll down the hill. Weird." said Squyres.
The spheres may have formed when molten rock was sprayed into the air by a volcano or a meteor impact. Or, they may be concretions, or accumulated material, formed by minerals coming out of solution as water diffused through rock, he said on a February 9 press conference.
One of the questions about the spherules was if they can be found in the deeper layers of the soil on Mars. When Opportunity dug her first trench (sol 23), pictures of the lower layers showed similar round spherules. But this time they had a very shiny surface, that created strong glints and glares. "They appear shiny or polished," said Albert Yen, science team member, during a press conference on February 19. He said: "Data will hopefully help us figure out what's altering them." At the same press briefing, Dr. Squyres noted this as one of the main question: "Where did those spherules come from, dropped from above or grown in place?"
The resulting trench -- the first dug by either Mars Exploration Rover -- is about 50 centimeters (20 inches) long and 10 centimeters (4 inches) deep. "It came out deeper than I expected," said Dr. Rob Sullivan of Cornell University, Ithaca, N.Y., a science-team member who worked closely with engineers to plan the digging.
Two features that caught scientists' attention were the clotty texture of soil in the upper wall of the trench and the brightness of soil on the trench floor, Sullivan said.
By inspecting the sides and floor of a hole it dug on Mars, NASA's Opportunity rover is finding some things it did not see beforehand, including round pebbles that are shiny and soil so fine-grained that the rover's microscope can't make out individual particles.
"What's underneath is different than what's at the immediate surface," said Dr. Albert Yen, rover science team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Opportunity digs a trench
The rover alternately pushed soil forward and backward out of the trench with its right front wheel while other wheels held the rover in place. The rover turned slightly between bouts of digging to widen the hole. "We took a patient, gentle approach to digging," Biesiadecki said. The process lasted 22 minutes.Timeline
The timeline can be found at MER-B timelineRelated articles
External References
External links
