The first images taken by Curiosity after operations were restored shows Mount Sharp with the arm and instrument turret in the midst of delivering a triple dose of powered rock to SAM for a more intense search for organic carbon. Credit: NASA/JPL-Caltech/MSSS/ Marco Di Lorenzo /Ken Kremer.com

The discovery of box-like geologic structures on Mount Sharp centered in Curiosity's Gale crater landing site, is raising interest for rover exploration as potentially habitable for past life on Mars.

New studies also indicate that three deep lakes existed in Gale crater eons ago, increasing the potential for lake dwelling microbial life to have existed in those environments as well.

The science and engineering teams for the rovers Curiosity and Opportunity are winding down operations in preparation for solar conjunction between April 4 and May 1, when the Sun blocks Earth's view of Mars. No significant commands can be sent to or received from the two rovers during that period.



Curiosity's left front and middle wheels are shown on rover during check of cameras after switch to B-side computer. Credit: NASA/JPL-Caltech/MSSS

Mars (and the rovers) are now 223 million miles (359 million km.) away from Earth. The same goes for the NASA Mars Reconnaissance Orbiter and Odyssey orbiter along with the European Space Agency Mars Express all circling Mars to acquire their own data sets while relaying communications from the rovers back to Earth. Their communications will also be affected.

Curiosity is just reinitiating operations from its late February computer memory snafu, at the same time it is being programmed for minimal activity for the solar conjunction.

"We are back to full science operations," said Curiosity Deputy Project Manager Jim Erickson of NASA's Jet Propulsion Laboratory, Pasadena, Calif.



Closer in image of manipulator arm shows the Yellowknife Bay mudstone lake bottom type terrain where Curiosity will roam further to find new drilling target after May 1. Credit: NASA/JPL-Caltech/MSSS/ Marco Di Lorenzo /Ken Kremer.com



One of the major operations before solar conjunction was the March 23 delivery by robot arm of a triple dose of drilled rock sample to the Sample Analysis at Mars (SAM) instrument for processing .

The Goddard Space Flight Center's SAM team hopes this triple dose will boost the signal strength of organic carbon molecules contained within the rock powder, or at least provide more insight to the simple organic molecules that SAM found during two processing runs in February also using the initially drilled powder.

One aspect of ramping-up activities after repairing the A-side BAE Systems Rad750 computer memory and switching the B-side computer to prime, has been to check the six engineering cameras that are hard-linked to that B-side machine.



Close up of Curiosity's 60 lb. multi talented instrument turret shows drill bit and its standoff prongs at center, with dust removal tool brushes at top and sample containment and delivery system at bottom. Credit: NASA/JPL-Caltech/MSSS.

The rover's science instruments, including five science cameras, can each be operated by either the A-side or B-side computer, whichever is active. However, each of Curiosity's 12 engineering cameras is linked to just one of the computers.

The engineering cameras are the Navigation Camera (Navcam), the Front Hazard-Avoidance Camera (Front Hazcam) and Rear Hazard-Avoidance Camera (Rear Hazcam). Each of those three named cameras has four cameras on it: two stereo pairs of cameras, with one pair linked to each computer. Only the pairs linked to the active computer can be used.

"This was the first use of the B-side engineering cameras since April 2012, on the way to Mars," said JPL's Justin Maki, team lead for these cameras. "Now we've used them on Mars for the first time, and they've all checked out OK."

Once past conjunction, the first major priority will be to locate a second suitable rock to drill. Scientists hope to run to ground the Yellowknife carbon story, so Curiosity can begin to rove toward Mount Sharp by early June and reach its flanks by January, 2014.



Large geologic box-like structures discovered by the Mars Reconnaissance Orbiter on Mount Sharp 2,887 ft. (880 m) above Curiosity could have possessed habitable conditions, and the mission team hopes the rover will eventually climb to reach them. Blue star denotes spine of feature. Credit: NASA/University of Arizona/JPL-Caltech.

Extensive Mars Reconnaissance Orbiter and Odyssey imaging of Gale Crater as part of landing site selection made the discovery of large "boxwork" geologic structures on Mount Sharp. They are positioned 2,887 ft. (880 m) above Curiosity on the crater floor, a location rover drivers hope to reach in the years ahead.

There are a "set of large-scale boxwork structures in a sedimentary layer on Mount Sharp", Curiosity Project Scientist John Grotzinger and planetary geologist Kirsten L. Siebach, both of Caltech told the Lunar and Planetary Science Conference (LPSC) in Houston last week.

"They are indicative of extensive groundwater cementation and represent a possibly habitable environment where organic molecules may have been preserved," they told the LPSC.

"Mapping of the structures is used to [define] a minimum volume of water at this site, which is recommended for Curiosity's future traverse" up Mt. Sharp, they said.



Closer view of Mount Sharp's "Boxwork" formations from Mars orbiter shows geologists how they were cemented together with ample water that could have made the site habitable. Credit: NASA/University of Arizona/JPL-Caltech.

As imaged from above by the Mars Reconnaissance Orbiter, the boxwork structures look like building frames without their roofs. But to the dismay of hucksters trying to convince Earthlings that intelligent Marians built them, they are simply geological formations.



They are fascinating however. The stratigraphic layer with box-like features is approximately 131 ft. (40 m ) thick, according to Grotzinger and Siebach.

"The fracture network is expressed as light-toned ridges separated by shallow depressions filled with dark windblown sediment. The ridges average 13-16.4 ft. (4-5 m) in width and are sometimes marked by a thin dark strip down the center of the ridge. Hollows are up to 1.6 ft. (0.5 m) deep, but can be separated from the ridges by steep walls up to 11.5 ft. (3.5 m) deep," said Grotzinger and Siebach.



Mars map shows Gale Crater location of Curiosity (right) with other potential future landing zone cited by name along with position of older landers and rovers. The Map uses color to convey heights with blue the lowest terrain. Credit: NASA/JPL-Caltech

The features are "boxwork structures, formed when [natural] cements filled existing pore spaces and fractures in already fractured rock, and these cements were left as topographic ridges after erosion. Boxwork structures on a smaller scale were first described in Wind Cave National Park, South Dakota," they said.

The amount of water required to create such large cemented structures is large enough to create at least part of the elements needed for a habitable environment, the two geologists indicated.

Gale's Crater's Lakes

While only the Yellowknife Bay area is found to have been "officially habitable" and is often characterized as an ancient lakebed, researchers believe they have uncovered evidence for three larger lakes in the history of the Gale crater that is about 100 mi. (161 km.) in diameter.



Graphic depicts large lake that overtopped Gale crater billions of years ago turning the top of Mount Sharp into an island. Credit: NASA/JPL-Caltech.

Curiosity co-investigator William Dietrich, of the University of California, Berkeley along with Marisa Palucis, also of UC Berkeley, and several other Mars researchers presented new evidence at the LPSC about three probable lake levels that occupied large portions of Gale crater billions of years ago and the possibility of former shallow lakes near the landing area itself.

The evidence for former lake levels consists of deltas, morphologic changes from canyons to local fan deposits, and topographic benches.

Those lakes and the evidence they left behind are:

Highest Level Lake: There is imagery from orbit as well as from Curiosity's high resolution color Mastcam camera that indicate a large lake initially filled much of Gale crater overtopping the crater rim and leaving the top 15% of Mount Sharp an island.





More recent although still billions of years old smaller lake was 2,133 ft. (650 m) deep and left evidence of its presence on southwest area of Gale crater. Credit: NASA/JPL-Caltech.

A 2,133 ft. (650 m.) deep lake: Citing earlier work by Dr. Ross Irwin, a Smithsonian National Air & Space Museum geologist, Dietrich and Palucis told the LPSC that imagery shows that a 328 ft. (100 m) high dark toned delta exists in the southwestern corner of Gale crater.

"The delta level roughly corresponds to the lower ends of inverted channels on the south side of Mt. Sharp and to a distinct bench on the northeastern side of the crater. A lake occupying current topography to this height would have covered about 2,251 square miles (5,830 square km.) with a mean depth of 2,133 ft. (650 m), according to Dietrich and his colleagues.

Boxwork level lake 558 ft. (170 m) deep: The authors told the LPSC that another lake left indications of a shoreline at about the same level where the box-like features exist. Tracing the lake's elevation on Mount Sharp and the walls of Gale crater indicates that this lake would equate to a 250 mi. (400 km.) circumference lake that was 558 ft. (170 m) deep confined to the northern and eastern sides of Mt. Sharp.



Rover orifice to SAM instrument provided a handy target to sharpen focus setting on the Mars Hand Lens Imager. Credit: NASA/JPL Caltech.

"The simplest interpretation of this succession of lake levels is that the crater filled with water and then the lake level progressively fell, perhaps stalling at two levels long enough to create a topographic record of the shoreline. The two lower deep lakes are marked by deltas at the mouth of the large canyon entering from the south, hence the southern uplands likely served as a source of water as well as sediment," said Dietrich and Palucis.

"The three high lake levels would have caused saturation of the deposits in Mt. Sharp and in the crater walls. As lake levels in Gale decreased, the low area immediately adjacent to the Curiosity landing site would have been one of the last areas to dry out," they believe.

Editors Note: With both Curiosity and Opportunity going into solar conjunction, CuriousMars will also take a hiatus.

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