Wednesday, September 4, 2013

November 2006 HiRISE Image Captures Youthful Ada Crater


Summary: A November 2006 HiRISE image captures youthful Ada Crater in the early months of the Mars Reconnaissance Orbiter’s (MRO) primary science phase.


Detail shows sharply-defined Ada Crater’s youthfulness and the crater’s enigmatic two-toned bedrocks and scalloped appearance; north is up; NASA image PSP_001348_1770; NASA ID PIA09372; image addition date 2006-11-29; image credit NASA / JPL / Univ. of Arizona: May be used for any purpose without prior permission, via NASA JPL Photojournal

A November 2006 HiRISE image captures youthful Ada Crater on Meridiani Planum in the early months of the Mars Reconnaissance Orbiter’s (MRO) primary science phase.
The Mars Reconnaissance Orbiter launched Friday, Aug. 12, 2005, at 11:43:00 Coordinated Universal Time (7:43 a.m. Eastern Daylight Time). The spacecraft reached its science orbit 13 months later, after cruising for seven months and aerobraking (reducing velocity via planetary atmospheric drag) for six months, according to the National Aeronautics and Space Agency’s (NASA) Mars Exploration Program website.
The HiRISE (High Resolution Imaging Science Experiment) camera numbers among the instruments carried onboard the Mars Reconnaissance Orbiter. The NASA Mars Exploration Program webpage on HiRISE describes the camera as “. . . big and powerful . . .” The camera’s image resolution capability allows for distinguishing objects as small as 3 feet (approximately 1 meter) in size. Features “. . . as small as a kitchen table . . .” have clear discernibility “. . . in images covering swaths of Mars’ surface 3.7 miles, or 6 km wide . . .”
The NASA Jet Propulsion Laboratory (JPL) Photojournal website added an image (image number PSP_001348_1770) of Ada Crater on Nov. 29, 2006. The HiRISE camera obtained the image on Nov. 9, 2006. The image is centered at minus 3.1 degrees south latitude, 356.8 degrees east longitude.
The HiRISE camera took the image at a target site range of 265.9 kilometers (166.2 miles). The Photojournal post calculates the image scale for this distance at “. . . 26.6 cm / pixel (with 1 x 1 binning) so objects ~80 cm across are resolved.”
The NASA JPL Photojournal post describes the image as capturing “. . . the youthful and enigmatic Ada crater and its fresh ejecta on the southern bounds of Meridiani Planum.” Ada’s characteristics of “ . . . well-developed and sharp crater morphologic features with no discernible superimposed impact craters . . .” attest to the crater’s freshness, or youthfulness.
The Nov. 9, 2006, HiRISE image confirmed NASA’s prior suspicion of Ada’s youthfulness. Primary structures in Ada’s fresh ejecta appeared in images obtained by the Mars Global Surveyor (MGS) robotic spacecraft’s Mars Orbiter Camera (MOC). Ada’s possession of a “. . . thermally distinct ejecta blanket . . .” was discerned via the Mars Global Surveyor’s Thermal Emission Spectrometer (TES) mapping. Spectral mapping by the 2001 Mars Odssey orbiter’s Thermal Emission Imaging System (THEMIS) revealed that “. . . the area surrounding the crater had been extensively swept clean of the surface deposit (possessing a Fe-rich mineral known as hematite) known to drape Meridiani Planum.”
Why does the NASA JPL Photojournal post describe Ada as “enigmatic”? The youthful crater’s “. . . interior crater morphology is what makes Ada so enigmatic . . .” Ada’s interior appears to consist of “. . . two craters (i.e., a smaller crater nested in a larger one).”
One explanation for Ada’s “. . . ‘nested’ crater-in-crater appearance . . .” could be the interior ledge’s formation by the slippage of bedrock down the crater wall. The problem with this possibility is that the ledge’s darker tone varies from the light tone of the upper crater wall’s exposed bedrock.
The presence of two differently toned rock types suggests Ada’s sampling of “. . . two distinct rock types from the subsurface.” The existence of the two distinctive bedrocks constitutes a significant clue. The crater’s “. . . strange appearance . . .” may track to “. . . the difference in strength between these two rock types . . .”
The “scalloped” appearance of Ada’s wall rock and rim also bespeaks the crater’s engigmatic quality. Downslope movement of crater wall material and erosion cause the rim’s distinctive scalloped shape.
The HiRISE camera obtained the Nov. 9, 2006, image of Ada Crater at 3:32 p.m. local Mars time. Illumination of the scene from the west, at a solar incidence angle of 56 degrees, places the sun at about 34 degrees above the horizon. The NASA JPL Photojournal post specifies: “At a solar longitude of 132.8 degrees, the season on Mars is Northern Summer.”
The takeaways for the November 2006 HiRISE image’s capture of Ada Crater’s youthfulness are that Ada’s “well-developed and sharp” features and absence of superimposed impact craters express the crater’s freshness; that Ada’s enigmatic aspects include an apparent interior “nesting” of two craters, two differently-toned bedrocks and scalloping of Ada’s wall rock and rim; and that the image confirms prior indications of fresh ejecta from Ada.

Complete image of Ada Crater obtained Nov. 9, 2006, at 3:32 p.m. local Mars time, during Martian Northern Summer, by NASA Mars Reconnaissance Orbiter’s (MRO) HiRISE camera at distance of 265.9 kilometers (166.2 miles); NASA image PSP_001348_1770; NASA ID PIA09372; image addition date 2006-11-29; image credit NASA / JPL / Univ. of Arizona: May be used for any purpose without prior permission, via NASA JPL Photojournal

Acknowledgment
My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:
Detail shows sharply-defined Ada Crater’s youthfulness and the crater’s enigmatic two-toned bedrocks and scalloped appearance; north is up; NASA image PSP_001348_1770; NASA ID PIA09372; image addition date 2006-11-29; image credit NASA / JPL / Univ. of Arizona: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA09372
Complete image of Ada Crater obtained Nov. 9, 2006, at 3:32 p.m. local Mars time, during Martian Northern Summer, by NASA Mars Reconnaissance Orbiter’s (MRO) HiRISE camera at distance of 265.9 kilometers (166.2 miles); NASA image PSP_001348_1770; NASA ID PIA09372; image addition date 2006-11-29; image credit NASA / JPL / Univ. of Arizona: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA09372

For further information:
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Available @ https://planetarynames.wr.usgs.gov/Feature/14182
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Available @ https://photojournal.jpl.nasa.gov/catalog/PIA09372
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