Astronauts often react with awe when they see the curvature of the Earth below the International Space Station. Now, Mars scientists are getting a taste of what that’s like, thanks to NASA’s 2001 Odyssey orbiter, which began its 22nd year at the red planet last month, on Oct. 24.
The spacecraft captured a series of panoramic images showcasing the curving Martian landscape below gauzy layers of clouds and dust in the atmosphere above. Stitched end to end, the 10 images offer not only an unfamiliar, and stunning, view of Mars, but also one that will help scientists gain new insights into the Martian atmosphere.
The spacecraft took the images in May from an altitude of about 400 miles (644 kilometers) — not too much higher than the space station flies above Earth: 250 miles (402 kilometers).
“If there were astronauts in orbit over Mars, this is the perspective they would have,” said Jonathon Hill, research specialist at Arizona State University's School of Earth and Space Exploration, operations lead for Odyssey’s camera, called the Thermal Emission Imaging System, or THEMIS.
“No Mars spacecraft has ever had this kind of view before,” he said.
How it was done
The reason the view is so uncommon is because of the challenges involved in creating it. Engineers at NASA's Jet Propulsion Laboratory and Lockheed Martin Space (which built Odyssey and co-leads day-to-day operations) spent three months planning the operation, which centered on Odyssey’s infrared THEMIS camera.
THEMIS’s sensitivity to warmth enables it to map ice, rock, sand and dust, along with temperature changes, on the planet’s surface.
It can also measure how much water ice or dust is in the atmosphere, but only in a narrow column directly below the spacecraft. That’s because THEMIS is fixed in place on the orbiter so that it usually points straight down.
Mission scientists wanted a more expansive view of the atmosphere. Seeing where those layers of water-ice clouds and dust are in relation to each other — whether there’s one layer or multiple layers, or whether they’re stacked on top of each other — helps them improve models of Mars’ atmosphere.
“I think of it as viewing a cross section, a slice through the atmosphere,” said Jeff Plaut, Odyssey’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California, which leads the mission. “There’s a lot of detail you can’t see from above, which is how THEMIS normally makes these measurements.”
Because THEMIS can’t pivot, adjusting the angle of camera requires adjusting the position of the spacecraft. In this case, the team would need to rotate the orbiter almost 90 degrees while making sure the sun would still shine on its solar panels but not on sensitive equipment that could overheat. The easiest orientation turned out to be one where the orbiter’s antenna pointed away from Earth. That meant the team would be out of communication with Odyssey for several hours until the operation was complete.
Over the moon
To make the most of their effort, the mission also captured imagery of Mars’ little moon, Phobos. This marks the seventh time in 22 years that the orbiter has trained THEMIS on the moon in order to measure temperature variations across its surface.
“We got a different angle and lighting conditions of Phobos than we’re used to,” Hill said. “That makes it a unique part of our Phobos set.”
Such details provide insight into the composition and physical properties of the moon. Further study could help settle a debate over whether Phobos, which measures about 16 miles (25 kilometers) across, is a captured asteroid or an ancient chunk of Mars that was blasted off the surface by an impact.
NASA is participating with JAXA (the Japanese Space Agency) in a sample return mission to Phobos and its sister moon, Deimos, called Mars Moon eXplorer, or MMX. Odyssey’s Phobos imagery will be helpful to scientists working on both missions.
More about the mission
Regents Professor Phil Christensen of ASU’s School of Earth and Space Exploration is the principal investigator for the 2001 Mars Odyssey THEMIS instrument. THEMIS was built and is operated by Arizona State University in Tempe. The prime contractor for the Odyssey project, Lockheed Martin Space in Denver, developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of Caltech in Pasadena.
This press release was written by Andrew Good from Jet Propulsion Laboratory, with contributions from Kim Baptista from ASU's School of Earth and Space Exploration.
Top photo: This unusual view of the horizon of Mars was captured by NASA’s Odyssey orbiter using its THEMIS camera in an operation that took engineers three months to plan. It’s taken from about 250 miles above the Martian surface — about the same altitude at which the International Space Station orbits Earth. Photo courtesy NASA/JPL-Caltech/ASU
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