April 24, 2024

The Inside Story of How NASA’s Odyssey Saw Mars in a New Way

“This unusual view of Mars’ horizon was captured by NASA’s Odyssey orbiter using its THEMIS camera, in an operation that took engineers three months to plan. It was taken about 400 kilometers above the Martian surface – approximately the same altitude at which the International Space Station orbits Earth.” | Credit: NASA/JPL-Caltech/ASU

NASA’s Odyssey orbiter captured a never-before-seen view of Mars, mimicking the perspective astronauts on Earth have from the International Space Station.

PetaPixel We discuss the achievement and technology that made it possible with Jeffrey Plaut, the Odyssey science project at NASA’s Jet Propulsion Laboratory (JPL) in California. Plaut has been with Odyssey for the entire life of its mission, approaching its 23rd year in Mars orbit.

Given that the Odyssey probe has been in orbit around Mars since October 24, 2001, why did the team wait so long to capture images like this? Plaut explains that he and the team need to return to NASA every few years with a mission plan and goals. This has numerous consequences.

This is an animated series of images showing Phobos, one of Mars’ two moons, moving across the sky. Phobos was also photographed while Odyssey was pointed towards the horizon. | Credit: NASA/JPL-Caltech/ASU

Perhaps most important, a mission team must convince the powers that be that the mission deserves additional time and funding. Although an original mission plan may include a long operational window, it is not certain that a mission will last as long as intended, and many missions have lasted much longer than initially expected.

These semi-regular meetings with NASA also mean that a mission team must follow through on the plans it offers when requesting more time and money. Every NASA mission must have valid scientific objectives and deliver on its promises.

Crop of the new THEMIS image of Mars | Credit: NASA/JPL-Caltech/ASU

In the case of Odyssey and its new orbital images, the team had to take these photos because they said they would when they submitted their mission plan to NASA. However, just because the photos were necessary to fulfill a promise doesn’t mean the photos are normal, because they aren’t.

“Every few years, we need to come up with a plan for what we will do scientifically in the next few years of the mission. At the moment, we are in a three-year cycle”, says Plaut PetaPixel. “A few years ago, we had to write a proposal document to NASA to continue the Mars Odyssey mission for another three years. Among the things we included in this proposal were new types of observations, including exactly this.”

By “this,” Plaut refers to the complex planning and image capture that resulted in the new views of Mars, which include “pointing the spacecraft at the limb, tracking the horizon to observe cloud structures, and observing the surface in the foreground.” to see how this perspective has changed our understanding of thermal emission from the surface and atmosphere. These things were in our proposal and we are committed to achieving them.”

The scientific community and the world are better for it, nothing less. In addition to checking a critical box on his to-do list, his team’s achievement means a lot to Plaut.

“It’s one of those things where I love doing this kind of work, because it’s super cool. We are looking at Mars, a different planet, in a way that no one has ever looked at before,” she explains enthusiastically.

“And that’s always a very exciting aspect of being a planetary scientist. No human eyes have actually been placed on this part of the solar system in this specific way before, and we are learning and seeing things in a different way for the first time. So that’s really cool and it gets you excited and makes you come back to work every day when you can do things like that.”

Crop of the new THEMIS image of Mars | Credit: NASA/JPL-Caltech/ASU

This is a vital point to focus on. Odyssey looked at Mars in a way no imager had ever done. Furthermore, achieving this feat was not simple at all.

The Odyssey orbiter has a highly specialized camera on board called “THEMIS,” which stands for Thermal Emission Imaging System. The camera was designed with a specific purpose in mind: it was built to measure thermal emissions, hence the name, on the Martian surface to determine different mineral compositions on the planet’s surface and how these minerals and the planet’s overall topography and geology relate. each other.

Without going too deep, the nature of the camera means that, unlike something like a normal digital camera, which resolves details thanks to visible light, THEMIS measures non-visible light – specifically infrared wavelengths. If anyone has seen thermal night vision goggles before, this is similar to how THEMIS works.

The image at the beginning of this article may look “normal”, for lack of a better term, but it is far from it. The craters, bumps and ripples on the surface are only visible because of the way Mars’ surface aberrations affect the way infrared wavelengths, or heat, travel from the planet’s surface to THEMIS.

“Basically, [THEMIS] provides images of the temperature of any target you are looking at. This week’s story is about this observation we made a few months ago, where we pointed the camera not down toward the surface where it’s normally pointed, but completely to the side. So it captured the foreground of the terrain up to the horizon and then the part of the sky above the horizon that contains the cloud layers,” explains Plaut.

“The colors in the foreground are not that significant,” adds Plaut, noting that the image processing team focused mainly on the colors of the clouds above the Martian surface. The image is constructed from three different infrared color channels, all well outside the spectrum that human eyes can see, so it is a false color image. THEMIS has nine different thermal infrared bands that it can use to fulfill its mineral spying mission.


The same reason THEMIS is so adept at assessing mineral compositions on the planet’s surface is also the reason it is able, with this new distorted view of the Red Planet’s atmosphere, to determine something about the chemicals in the clouds above. Mars.

“But another capability of having these multiple channels is being able to observe the atmosphere and distinguish the composition of materials in the clouds. We selected the bands so that they distinguished several different types of clouds and ended in colors that are kind of intuitive because they would like the visible colors, which are the lower layers of dust that hug the ground. Here are these reddish-brown layers. They are clouds of dust. And then these higher-altitude clouds, which are bluish, are water-ice clouds, similar to the clouds in Earth’s atmosphere,” says Plaut.

Plaut is an invaluable resource not only for understanding Odyssey’s mission and Mars itself, but also for fully appreciating the latest images.

While some people might see the new image and think, “Oh, it’s just another image of Mars,” there’s a lot more going on here that is scientifically interesting and fascinating from an imaging technology perspective.

Looking at the terrain, Plaut explains that what people see is the temperature. “It looks like a photograph lit by the Sun, and they are all craters. You can see that many of them have a light edge and a darker edge. And that’s because the afternoon sun was or still shines on one side of the crater. We’re in a late afternoon orbit, and the Sun is very low in the sky, so it’s only illuminating half of the crater and the other half is in shadow, but you’re seeing the temperatures, that’s what the camera is sensitive to,” explains Plaut.

Crop of the new THEMIS image of Mars | Credit: NASA/JPL-Caltech/ASU

What THEMIS sees is not sunlight in the common sense, the way people see it, but the thermal effects of solar radiation.

“You’re seeing the hot side that’s still being lit or has recently been lit by the Sun, and it stays warm throughout the afternoon and through the night, and then everything kind of evens out in temperature. So a lot of what you’re seeing looks like a topographic image, but it’s actually a temperature image and topography controls temperature.”

“Now, there are some craters where there are bright spots, hot spots at the bottom of the crater… this is the result of these surfaces being a little different from their surroundings in the way they retain their heat. Then again, I think this part of the image takes place in the late afternoon or evening, around 6pm local time. And then some of these surfaces have been heating up all day and are still hot.”

What Plaut is saying here is that visible topographic detail is not the result of how visible light interacts with the surface of Mars, but how visible light interacts with the surface of Mars. Warm of the Sun reaches the planet, is retained by different minerals and soil compositions, and is affected by the roughness of sand and rock. Although the detail here reflects and is affected by sunlight, it does not show sunlight itself.

“So you see this daily cycle of temperature changes, and a lot of it depends on the material. We use that information in these thermal images to say, ‘Oh, is this a dusty area of ​​Mars? Is this a rock outcrop? Is this some kind of coarse sand or fine sand?’ And so apparently at the bottom of some of these craters there is some kind of probably thicker, higher density material that maintains its heat well into the afternoon or early evening compared to some of the surroundings that are darker and therefore have cooled down. more. .”

As is always the case, NASA missions represent incredible and crucial scientific work and demonstrate the many ways in which different imaging technologies can push the limits of human understanding even further.

Image credits: NASA/JPL-Caltech/ASU

Leave a Reply

Your email address will not be published. Required fields are marked *