NASA’s Mars Odyssey orbiter, currently in its 23rd year around the Red Planet, has given scientists a unique perspective. From an altitude of about 400 kilometres, the orbiter’s images offer an extraordinary view that reflects what astronauts might see if they were in orbit around Mars.
The spacecraft, equipped with the Thermal Emission Imaging System (THEMIS), captured a series of panoramic images showing the Martian landscape adorned with layers of clouds and dust.
The most remarkable thing that can be seen in this image, thanks to the fact that we are looking at the planet from an angle, is the structure of its beautiful clouds.
This is possible thanks to the THEMIS camera, which combines three channels of infrared data enabling us to see the difference between different types of clouds, including CO2 ice clouds, water ice clouds, and dust clouds.
Odyssey and THEMIS
Mars Odyssey mission was launched on April 7, 2001 and has been operational for 22 years, becoming the longest-running spacecraft ever sent to visit Mars. Next year, it will reach 100,000 orbits around Mars.
Its main goal was to create the first comprehensive map describing the distribution of various chemical elements and minerals that make up the Martian surface. After successfully completing its main science mission in August 2004, the orbiter continues its extended operations today. Acting as a vital communications relay, Odyssey supports the rovers and landers on Mars.
It also continues to analyse and map the Martian surface with its instruments, including the Thermal Emission Imaging System (THEMIS), the Gamma Ray Spectrometer (GRS) and the Mars Radiation Environment Experiment (MARIE).
Specifically, THEMIS is a heat-sensitive infrared camera that can map various features of Mars, including ice, rock, sand and dust, as well as temperature changes on the planet’s surface. It can also measure the amount of water ice or dust in the atmosphere, but only in a narrow column directly beneath the spacecraft. This is because THEMIS is fixed in position on the orbiter and usually points downwards.
A challenging imaging process
Creating this extraordinary view posed challenges for NASA’s Jet Propulsion Laboratory and Lockheed Martin Space, the authorities overseeing the mission. For three months, engineers meticulously planned the observations, considering the fixed nature of THEMIS on the orbiter.
Although the thermal camera was not adjustable to frame the horizon, the mission aimed to obtain a wider view of the Mars atmosphere, which required a unique spacecraft adjustment that had never been attempted before.
To achieve this, it was necessary to rotate the orbiter by almost 90 degrees, while ensuring that sunlight continued to illuminate the solar panels without affecting sensitive equipment that could overheat. The chosen orientation involved pointing the orbiter’s antenna away from Earth, causing a temporary communication blackout with Odyssey for several hours.
Obtaining this type of image allows scientists to see where the layers of water ice and dust clouds are in relation to each other, and to create a better model of Mars atmosphere.
“I think of it as viewing a cross-section, a slice through the atmosphere,” said Jeffrey Plaut, Odyssey’s project scientist at JPL. “There’s a lot of detail you can’t see from above, which is how THEMIS normally makes these measurements.”
Despite the technical complexities, the Odyssey mission intends to repeat this task in the future, capturing images of the Martian atmosphere in different seasons. These ongoing efforts aim to continuously improve our understanding of the Red Planet by providing more detailed and deeper data.
Over the Moon: Odyssey’s Exploration of Phobos
In addition to images of the Martian surface, to make the most of its efforts, the mission also captured new images of the small moon of Mars, Phobos.
This is the seventh time in 22 years that THEMIS has been pointed at the moon to measure temperature variations on its surface. The image offers a unique perspective and different illumination conditions, enriching the data set of Phobos and contributing to the understanding of its composition and physical properties.
The new images not only capture attention for their beauty, but also provide an in-depth view of the moon’s composition and physical properties. This contribution becomes crucial in the context of an ongoing discussion about Phobos, which measures about 25 kilometres in diameter: is it a captured asteroid or an ancient fragment of Mars ejected from the surface due to an impact?
The new images of Phobos represent a significant contribution to the Odyssey mission and will also be useful for the joint NASA-JAXA mission called Mars Moon eXplorer (MMX), which aims to bring back samples from Phobos and its twin, Deimos.
The Mars Odyssey orbiter still continues to amaze and contribute significantly to our understanding of Mars, offering an unprecedented perspective on the beauty and complexity of the Red Planet.