Mars Exploration Rover atmospheric imaging

MER atmospheric imaging page

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The Mars Exploration Rovers, Spirit and Opportunity, were sent to Mars primarily to investigate the geologic record of water in Mars' past. While actively exploring the Gusev crater (Spirit) and Meridiani planum (Opportunity) area, they have also taken time to investigate the atmosphere. The atmospheric investigation comprises imaging with the Panoramic Camera (Pancam) and with the Navigation camera (Navcam), and spectra from the Miniature Thermal Emission Spectrometer (Mini-TES). For more information about the rovers, their instruments, and the overall investigation, see JPL's Mars Exploration Rover Mission home page.

This site collects links to some of the specifically atmospheric imaging results. This page is intended to collect links to publicly available information. Other forums (for instance, the first two science articles from the atmospheric team, Smith et al. 2004 and Lemmon et al. 2004) are more appropriate for the discussion of detailed scientific results. For the purposes of this page, "atmospheric" really just means looking up. Astronomical observations (through the atmosphere) count. This is partly related to who does what on the whole team, but also to the commonality of observations. For instance, Sun image for dust monitoring are similar to those for Phobos eclipsing the Sun; twilight observations to study dust structure can also see Earth and meteors. The observations linked here are the result of work by not only the MER atmospheric science theme group, but of MANY individuals across the MER project.

The organization of the links below is simple: newer stuff is at the top. Enjoy.

"A moment frozen in time," sunset of Spirit's sol 489, 19 May 2005.

First, see the JPL press release, if you have not seen it. Or see the Planetary Photojournal archive. Then, see the high resolution versions, 1600x1200 JPEG (0.5 MB), or full TIF (3.7 MB) (image credit: "NASA/JPL/Texas A&M/Cornell". This is a public image available under the same terms as the version at the JPL site.) The "full-res TIFF" at Photojournal was made from a reduced-size JPEG. The previous link has the archival high-resolution TIF.

JPL's caption describes the image best, but here is some more technical info. The image was taken with Pancam's L2, L5, and L7 filters (infrared, green, and violet). So, the colors are real, but exagerated compared to what the eye would see. Some of the images were taken with "downsampling" the image to a smaller number of pixels. As with lossy compression (which was also used), restoration of the full image is imperfect, but losses are minimal with sky images like this. Also, the Sun moved between color images, so that was fixed by using the blue filter Sun image for all filters. Previous Sun images have shown that the Sun itself is actually very slightly blue as it sets, but the Sun was saturated in these images. A quick primer on Martian sky colors: the sky is yellow-to red toned, becuase that is the intrinsic color of the dust, due to iron oxides (aka, rust). The sky near the Sun, especially at sun-rise/set, is blue becuase some blue light is scattered and not absorbed by the dust. Blue light is scattered (through diffraction) into a much narrower range of angles than red light. The Sun itself is slightly blue for a different reason. In Earth's sky, blue optical depths are usually larger than red optical depths--the Sun ends up red at sunset. In Mars' sky, dust optical depth is larger for infrared and red light than for blue light. This effect is much weaker for Mars than for the Earth. As with Earth, it is also weather dependent: water ice hazes can raise the blue optical depth and neutralize the Sun's color.

Finally, an earlier image showed the Martian twilight shortly after sunset.

"Earth as seen from Mars," evening of Opportunity's sol 449, 29 April 2005.

Chances for night wake-ups are rare. In April 2005 it had been over a year since the only previous images of Earth from the surface of Mars were taken. In the interim, Earth passed behind the Sun and went from being a "morning star" to being an "evening star". See JPL's site. Sadly, the skies are currently too dusty to repeat this image, as Jupiter passes close to Earth in the night sky in June. The optimum time for multispectral observations of Earth would be June-September 2005, weather permitting.

Dust devils seen by Spirit on Gusev crater floor.

For the first year on Mars, no dust devils were seen. Since March 2005, they have been seen on numerous occasions. At that time, it was just becoming Spring in the southern hemisphere of Mars. During southern spring and summer, Mars is closer to the Sun than during the same sesons up north. This is Mars' dust storm season, roughly. The rovers had already started getting a taste of small local dust storms since just before New Years' eve. These storms left residual dust, so the skies were dustier than they had been anytime in the extended mission. In fact Opportunity had a few sols with more dust than she had ever seen before. Spirit later went through two storms with even more dust before Spring even officially started (22 March, coincidentally).

With the start of Spring and the spotting of the first dust devils, the rover team started a campaign of taking a series of still images to be combined into movies. Those movies are taken with Navcam, which has a larger field of view than pancam. The viewing geometry of looking down onto the plains for bright dust against a dark surface makes dust devil spotting relatively easy.

Astronomy update: Phobos and Deimos transits

The links to the original releases of Phobos and Deimos images as they transit across the face of the Sun (i.e., partial or annular solar eclipses) are below. The following images are artificially expanded in size and show Mars' moons in front of the Sun in 2004 and 2005. The next transit season will begin with Opportunity having another chance at Deimos around sol 700 or so (Jan '06).

Dust on Mars: Before and after

The Pancam team comapred dust on the rovers after about a year of operations on Mars, for Spirit and for Opportunity.

Water, frost, and clouds

December presentations at the American Geophysical Union conference had a focus on geology, of course, but also included a selecation of Opportunity's cloud images, frost, and even Mini-TES atmospheric results, here.

Additional cloud images had been shown in in November, in August, and in July.

Gusev's rim revealed

The amount of dust in the skies above Opportunity fell by more than half between landing and mid-winter. At Gusev, the fall off was more dramatic. Firstly, the amount of dust went down by a factor of 5; secondly, there were distant features made visible by the low dust load. Gusev's northern rim, and Ma'adim Vallis to the south.

The rovers become astronomers

Spirit observed the constellation Orion, Earth, and a meteor (that initially was thought to be a trail of light made by Viking Orbiter 2. Opportunity joined in the fun with images of Phobos and Deimos transiting in front of the Sun (this release also includes good ol' Mini-TES, with atmospheric observations coordinated with TES on Mars Global Surveyor.

Mars Sunset Clip from Opportunity Tells Dusty Tale

In the first of many sunset observations, Opportunity saw the sun fade into the dust rather than truly set. See JPL.