MER atmospheric imaging page
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.
Bonus Mini-TES
Mini-TES probes
atmospheric temperature and dynamics. But wait,
there's more.
Bonus feature: Mini-TES atmospheric team
What is Mini-TES doing looking up? Find out
here.
