NASA Mars Reconnaissance Orbiter Mars Color Imager MARCI View of Argyre Basin, Mars
MRO MARCI Release No. MARCI2-2, 13 April 2006
MARCI2-2a — MARCI Bands 3(600nm) / 1 (425 nm) / 6 (260 nm) and MOC WA (650nm/425 nm) composite  |
MARCI2-2b — Oblique perspective view of MARCI 3-band color [1 (425nm)/ 2 (500 nm) / 3 (600 nm)] All images credit: NASA/JPL/Malin Space Science Systems |
As part of the checkout of the Mars Reconnaissance Orbiter (MRO)
payload after the 10 March 2006 orbit insertion, the Mars Color
Imager (MARCI) acquired a seven band color wide angle view of Mars
on 24 March 2006. Illustrated here are some of these test images.
Note that the linear banding seen in these images
are artifacts resulting from incomplete removal of the detector pixel to
pixel variations. Such deviations from ground testing calibration are an
important reason for taking checkout images.
In the first figure (MARCI2-2a), three views acquired by
MRO MARCI are compared to a color composite of two views acquired
about 4 hours later by the Mars Global Surveyor (MGS)
Mars Orbiter Camera (MOC). MRO imaging occurred during the early
morning on Mars, while the MGS observations were made at around
2 PM local solar time. The region of Mars imaged by MRO on this
day was south of the Valles Marineris and includes the large Argyre
Basin, its interior plains, Argyre Planitia, and the mountains that
comprise the basin rim, Nereidum Montes to the northwest
(middle of images) and Charitum Montes to the southeast
(bottom of images).
The ultraviolet (UV) image (260 nm in MARCI2-2a) shows how
the planet appears in an ozone absorption band. Relatively darker
areas in this band normally will indicate the presence
of ozone, and relatively lighter areas will indicate the absence
of ozone. Water vapor on Mars is anticorrelated with ozone, meaning
that lighter areas can be used to track water vapor. The
term “relatively” is used here because
Mars itself is very dark in the UV owing to absorption of
UV light by iron-bearing minerals, and sunlight is deficient
in UV relative to visible light, so in general Mars will always
look dark in the UV. A second UV band on MARCI (not shown in
the figure above) at a longer wavelength allows these differences
to be quantified. The MOC wide angle image shows wispy, light
water-ice clouds to the northwest of Argyre in the afternoon,
but we cannot as yet correlate these clouds with the UV information
(especially because the times of day are different). When in its
final mapping orbit, MRO will view the same area as MGS separated
by only 1 hour, and such correlations will be much more direct.
The second picture (MARCI2-2b), shows a color composite made
from the MARCI red, green, and blue bands. It differs from the MOC wide
angle color composite because, to create a color image with MOC data,
we synthesize (fake) a green channel by adding the red and blue
channels together and dividing by two. The slightly greenish tint
of the MARCI image shows that the approximation used for MOC
images underestimates the amount of green. Further calibration
will be needed before
a “true” color image—as it would appear to a human
eye looking down from orbit—can be reconstructed from the
MARCI data.
For more details of how MARCI images are acquired and processed,
see the companion MARCI release,
MARCI2-3,
and be certain to examine the
15.6 Mbyte animated GIF movie.
The pictures shown here are the first views of Mars acquired
by the MRO MARCI. This is a re-flight of a similar instrument
that was aboard the Mars Climate Orbiter, which was lost
in September 1999 during its orbit insertion activity.
In the primary science phase of the MRO mission, MARCI
will routinely acquire daily global maps of the planet.
These data will be used to help track storms, monitor
clouds and water vapor, and track seasonal changes in
surface albedo (bright and dark) patterns and the polar caps.
Malin Space
Science Systems built and operates the MARCI onboard MRO at its facilities
in San Diego, California. The Jet Propulsion Laboratory operates the Mars
Reconnaissance Orbiter spacecraft with its industrial partner, Lockheed
Martin Astronautics, from facilities in Pasadena, California, and Denver,
Colorado.
