This is a sub-section of the “geometrically improved, color enhanced” version of the 360-degree panorama heretofore known as the “Gallery Pan”, the first contiguous, uniform panorama taken by the Imager for Mars Pathfinder (IMP) over the course of Sols 8, 9, and 10. Different regions were imaged at different times over the three Martian days to acquire consistent lighting and shadow conditions for all areas of the panorama.
When Pathfinder was send to Mars it mostly served as taxi for the small Sojourner rover. On July 4, 1997, Pathfinder with the Sojourner rover landed in Ares Vallis region of Mars is at 19.33 N, 33.55 W. The Ares Vallis region of Mars is a large outwash plain near Chryse Planitia. This region is one of the largest outflow channels on Mars, the result of a huge flood (possibly an amount of water equivalent to the volume of all five Great Lakes) over a short period of time flowing into the martian northern lowlands.
Pathfinder and Sojourner operated until communication was lost for unknown reasons on 27 September 1997.
The name Sojourner was chosen for the Mars Pathfinder rover from 3,500 entries for a Rover naming competition to select a heroine and submit an essay about her historical accomplishments. Valerie Ambroise, 12, of Bridgeport, Connecticut, submitted the winning essay about Sojourner Truth, a black reformist who lived during the Civil War era. An abolitionist and champion of women’s rights, Sojourner Truth, whose legal name was Isabella Van Wagener, made it her mission to “travel up and down the land,” advocating the rights of all people to be free and the rights of women to participate fully in society. The name Sojourner was selected because it means “traveler.”
On sol 2 drove off the ramp of the Pathfinder to begin her treck around the lander taking a close up look at the mars rocks strewn across the landscape.
The Sojourner rover is very small compared to the later rovers. No more than a big VCR (remember those?) on six-wheels. A small box measuring 65 cm in length, 48 cm in width, 30 cm in height and weighing only 10.5 kg. It could drive as fast as one centimeter per second (Curiosity is 4 times as fast). Ofcourse it never drove that fast. The rover was only inched forward as we were all to nervous about breaking it, if we wanted to do anything too fast.
Sojourner travelled approximately 100 metres in total, never more than 12 metres from the Pathfinder station. During its 83 sols of operation, it sent 550 photographs to Earth and analyzed the chemical properties of 16 locations near the lander. The rover was only active during the day and ‘slept’ at night. The rover made measurements of the elements found in those rocks and in the martian soil, while the lander took pictures of the Sojourner and the surrounding terrain.
Note: The day on Mars is called ‘sol’ to distinguish it from a day on Earth; a sol is 24 hours, 39 minutes and 35 seconds long.
As driving around on Mars was totally new to us on Earth, and as we really could not drive large distances with this first mars rover, scientist named the rocks Sojourner visited after famous cartoon characters. The first rock she visited was named Yogi (after the animation character Yogi bear from Jellystone Park = Yellowstone National Park)
The rock was the first on Mars found to be made of basalt, which suggests previous volcanic activity in the region as basalt is an igneous rock. Igneous rock is formed through the cooling and hardening of magma or lava. The smoothness of the surface also suggested the past existence of water in the region. Yogi was analyzed by the Alpha Proton X-ray Spectrometer (APXS) to determine its composition.
At first measurements of Yogi suggested that it had been deposited to the site by floods, as it seemed to be of different composition than the rock Barnacle Bill (analysed on Sol 3). Later scientist realised that Yogi probably had a coating of dust, but was similar to the rock Barnacle Bill.
Calculations suggest that the two rocks contain mostly the minerals orthopyroxene (magnesium-iron silicate), feldspars (aluminum silicates of potassium, sodium, and calcium), quartz (silicon dioxide), with smaller amounts of magnetite, ilmenite, iron sulfide, and calcium phosphate.
On the back, near the APXS and rotated by 90° Sojourner carried a colour camera (one of the three cameras she had) to provide images of the APXS’s target area and the rover’s tracks on the ground. The camera had sensitivity to green (12 pixels out of the 16 total pixels in each 4×4 pixel block), red (2 pixels), and blue (2 pixels), with the blue-sensitive pixels being sensitive to infrared as well. This sensitivity to infrared by all three cameras was due to the fact that they all had zinc-selenide lenses, which blocked blue light below 500 nm, thus only allowing infrared wavelengths to reach the blue pixels.
The rover also had two black & white 0.3-megapixel cameras on the front (768 horizontal pixels × 484 vertical pixels configured in 4×4 pixel blocks), coupled with five laser stripe projectors, which enabled 3D images to be taken along with measurements for hazard detection on the rover’s path.
The cameras made it possible for us to view the Martian surface from just a few millimeters to many hundreds of meters. This helped considerably in understanding the evolutionary history of the rocks and surface.
All three cameras were CCDs manufactured by Eastman Kodak Company, and were controlled by the rover’s computer. They all had auto-exposure and bad pixel handling capabilities. Each of the transmitted images came with an image header giving information about the size, resolution, number of colours of the image. The rover could compress the front cameras’ images using the block truncation coding (BTC) algorithm. Compressing the images of the back colour camera was only possible, if the colour information was discarded. The cameras’ optical resolution was sufficient for resolving 0.6 cm details across a 0.65 m range
On Sol 3 Sojourner drove up to “Barnacle Bill“. The APXS took ten hours to make a full scan of the sample. It found all the elements except hydrogen. The APXS results told us that “Barnacle Bill” is much like Earth’s andesites, which confirm a volcanic past of this region of Mars. The discovery of andesites shows that some Martian rocks have been remelted and reprocessed. On Earth, Andesite forms when magma sits in pockets of rock while some of the iron and magnesium settle out. As a result of this process the final rock contains less iron and magnesiums and more silica.
Another rock, named Moe, was found to have certain marks on its surface, demonstrating erosion caused by the wind.
Most rocks analyzed showed a high content of silicon.
The Sojourner rover’s Alpha Proton X-ray Spectrometer (APXS) is shown deployed against the rock “Moe” on the afternoon of Sol 64 (September 7). The rocks to the left of Moe are “Shark” (left of Sojourner) and “Half Dome” (behind Sojourner). They were previously measured by the APXS.
In the ‘Rock Garden’ Sojourner found crescent moon-shaped dunes, which are similar to crescentic dunes on Earth. Such Barchan dunes are found all over Earth, a.o. in Great Sand Dunes National Park in Colorado.
(left) Portions of Sojourner’s Alpha Proton X-Ray Spectrometer (APXS), a deployment spring, and the rock Barnacle Bill are visible in this color image. The image was taken by Sojourner’s rear camera, and shows that the APXS made good contact with Barnacle Bill. Portions of Sojourner’s Alpha Proton X-Ray Spectrometer (APXS), a deployment spring, and the rock Barnacle Bill are visible in this color image. The image was taken by Sojourner’s rear camera, and shows that the APXS made good contact with Barnacle Bill.
The Mars Pathfinder Sojourner Rover was placed in the Robot Hall of fame in 2003 for being the first to explore another planet. Sojourner had been the first thinking robot equipped with sophisticated laser eyes and automated programming, reacting to unplanned events on the surface of another planet. A hazard avoidance system set the rover apart from all other machines that previously explored space.
Sojourner paved the way for the Mars Exploratation Rovers Spirit and Opportunity that have been exploring Mars since 2004 and for the Curiosity rover.
The final Pathfinder mission results were described in a series of articles in the journal Science, issue December 5, 1997.
(bel0w) Mars Pathfinder display in Paris, 2001 (personal foto archives Artemis Westenberg)
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