Curious Mars


CuriousMars: California Dreamin' on a Martian Day

Spectacular panorama by the Mars rover Curiosity shows nuclear powered RTG at far left while the robotic arm places the Alpha Particle X-ray Spectrometer on the ground. Mt. Sharp is in background and rover wheels visible at far right are from mosaicing separate images. Differences in sky brightness are from images in mosaic being taken at different times of day. Credit: NASA/JPL/Caltech/ Mark Di Lorenzo and Ken Kremer.com

There are already plenty of stars around Malibu, California, but could the place be actually like the planet Mars? The NASA rover Curiosity is about to find out.

Two California locations, including an area near the Santa Monica Mountains stretching north from Malibu, were searched in late January for rocks strikingly similar to the Martian rocks that Curiosity is about to drill into on Mars. The samples found are completing final tests for use in assessing the success of the first rock drilling and sampling on another planet.

The drilling and analysis of samples from the inside of a Martian rock should be underway next week with the first shallow drilling tests as early as Feb. 2-4, according to Robert C. Anderson, a member of the Surface Sampling System (SSS) Team at the Jet Propulsion Laboratory, Pasadena, Calif.

The overall process is to result in samples collected from a rock depth of nearly 2 in. (5 cm.) where the rock should reveal secrets of what it is made of, how it formed, and whether any organic carbon, a building block for life, is present. That data will provide some evidence whether or not life ever had a chance to form in that location.


Curiosity's 60 lb. science instrument turret is placed on Martian surface by 7.5 ft. robotic arm. Turret has been rotated to place the Alpha Particle X-ray Spectrometer on rocks, about to be pierced by the drill, which is shiny circular plate with drill bit facing the 2 o'clock position. Credit: NASA/JPL/Caltech/ Mark Di Lorenzo and Ken Kremer.com

This will be an historic milestone in planetary exploration and the last big test of Curiosity's critical drilling and sampling hardware before the rover heads to Mt. Sharp, where the search will begin in earnest for organic carbon the primary mission goal.

"We are proceeding with caution in the approach to Curiosity's first drilling. This is challenging," said Daniel Limonadi, JPL's lead systems engineer for Curiosity's surface sampling and science system. It will be the first time any robot has drilled into a rock to collect a sample on Mars."

Anderson told CuriousMars that during their mountain foothills search, members of the
science team found what they were seeking; "mudstone", a fine-grained sedimentary rock whose original constituents were clays or mud that formed in water.

Many mudstone formations on Earth look very similar to the flat, veined, fine grained rocks at the Martian drilling site in images transmitted from the big rover.


Overall drilling area named John Kline is imaged from a different angle. The drilling area is more toward upper center of the broken terrain that looks like it could be mudstone formed by clays or mud in water. Credit: NASA/JPL/Caltech/ Mark Di Lorenzo and Ken Kremer.com

Curiosity researchers also searched an area near the Salton Sea, south of Palm Springs, looking for rocks rich in calcium sulfate that also form with water," says Anderson. The Salton Sea area rocks have chemistry similar to that detected by the rover's ChemCam laser and Alpha Particle X-ray Spectrometer (APXS) and microscopic imager instruments.

The main source of calcium sulfate is naturally occurring gypsum, which the 9 yr. old Mars Exploration Rover Opportunity found earlier on the opposite side of Mars, indicating abundant water was present there also.

The science team does not know what kind of rock chemistry and mineralogy they will find inside the Martian rocks of Gale Crater, but the California samples are being used as most representative of what the team expects to find and how that will affect drilling," Anderson told CuriousMars.

That's why they have been used in final Jet Propulsion Laboratory drilling tests this week before Curiosity begins drilling Martian rocks. Curiosity's arm will be drop the powdered samples into the rover's internal CheMin mineralogy laboratory and the powerful $80 million Sample Analysis at Mars (SAM) chemistry laboratory. SAM will search for carbon compounds and determine the abundances of different elements.


Curiosity's instrument turret is a marvel of packaging and robotics. Note center mounted rotating percussion chisel-like drill bit in center and large standoff prongs on either side of hub all pointing toward 4 o'clock position. Credit: NASA/JPL/Caltech

The Martian drilling location is named "John Kline" in memory of the Mars Science Laboratory's late deputy project manager who died in 2011.

The California sample rocks were first slowly heated to rid them of moisture making them more like dry Martian rocks. They were then placed in a JPL altitude chamber with a carbon dioxide atmosphere dropped to the same level as on the Martian surface, about 0.6% of Earth's mean sea level pressure.

An engineering version of Curiosity's percussion rotary chisel type drill was used to penetrate the California rocks to assess what percussion and rotational parameters to use and importantly to generate tailings that will be compared with those generated on Mars early in the drilling.

That comparison will be important for Anderson and two SSS colleagues to determine if deeper drilling, followed by sample acquisition can proceed safely as demonstrated by the test rocks in the JPL altitude chamber drilling exercises.


Rover's forward Hazcams near bottom of chasse look out from between Curiosity's front wheels to image the drill side of turret being placed on rock. Note how large standoff prongs make contact with surface first allowing drill to move in the center. Credit: NASA/JPL/Caltech

For Anderson, this part of the drilling preparation has been years in the making. When he joined the Curiosity program in late 2005 after service with the Spirit and Opportunity, he immediately began compiling a large library of Earth rocks possibly like what Curiosity would find on Mars.

All kinds of rocks from the rock library were drill tested for multiple parameters during the rover drill's early design, development and modification periods, until the operational design was finalized. A number of the precise drills were built for the Curiosity and ground testing. More than 10 calcium sulfate rocks and their cousins were characterized in detail because that is likely to be present in Martian rocks.

Detailed parameter options, like percussive force, rotational speed and sampling characteristics related to science were also documented for many more rock types in the library.


Robotic arm was used to elevate, then rotate turret so the strong brushes of the Honeybee Robotics Dust Removal Tool (DRT) can be inspected by the color Mastcam imager before it claws through the surface coating on another rock making data acquisition more effective . The "Bees" more than a decade ago designed and built Opportunity's Rock Abrasion Tool (RAT) in t that is still going strong on the opposite side of Mars. Credit: NASA/JPL/Caltech

As the actual drilling time neared this month, the science and SSS teams were looking at the latest Martian images from Curiosity and determined they could find even better analogs than in the rock library for the specific Martian rocks in view. So they again went into the field to get the new analog rocks and are now even more comfortable about drilling at the John Kline area.

MSL project management is maintaining strong oversight on all the pre drilling preparations, putting in "gates" or stopping points where specific requirements must be satisfied before progressing further.

"One thing about MSL management is they are very thorough in their decisions to put the gates in. They do not take any shortcuts," Anderson said. "This is a very precious resource on the surface of Mars. So we have to go through each of those gates and prove to the project management that we know what we are doing and we are pretty confident of the results," he said.

One major change, as of now, is that MSL management no longer believes the rover's sample transport hardware needs to be further swept with Mars dust to be generally free of contamination.


Internal workings of a Curiosity drill bit are annotated in the graphic. Credit: NASA/JPL

Therefore an earlier plan to drill three holes for contamination scrubbing has been dropped . Now only one hole is to be drilled before Curiosity heads to Mt. Sharp. The drill may indeed send some minor contamination into SAM, but the science team has quantified it and the SAM team sees no problem, said Anderson.

"But that may change," he said. "On Mars the only certain thing is uncertainty."

Key milestones being achieved in the final days before drilling are:

--Pre-load testing: This test was completed Jan 27 after the rover arm moved the drill to four different locations followed each time by the arm pressing the drill down using the mass of the rover to apply a specific downward force. The tests enabled engineers to check whether the amount of force applied to the hardware matches predictions for what would result from the commanded motions.

--Overnight pre-load test: Conducted Jan. 28, the drill and its standoff prongs were again lowered to the surface, and a pre-load maintained across a day/night temperature cycle with a high of about 32 deg. F (0 deg C) and low of -85 deg. F (-65 deg. C) "This test was done at lower pre-load values than we plan to use during drilling, to let us learn about the temperature effects without putting the hardware at risk," said Limonadi in a JPL release.

--Drill-on-rock checkout: This test will use the hammering action of Curiosity's drill briefly, without rotation of the drill bit, for assurance that the back-and-forth percussion mechanism and associated control system are properly tuned for hitting a rock. The rover's electronics enable a precise tuning of hammering force, applied to specific rock characteristics, said Anderson.

--The mini-drill: This will actually be the first drilling of a Martian rock, but not by much. It is only designed to produce a small ring of tailings powder on the surface of the rock while penetrating just 0.78 in. (2 cm.). This activity will not go deep enough to auger rock powder into the drill's sample-gathering chamber, Anderson told CuriousMars. "The purpose is to see whether the tailings are behaving the way we expect. Do they look like
dry powder? That's what we want to confirm," said Limonadi.


Curiosity Mastcam image of drill bit shows percussion bit at center flanked by treaded prongs to hold the bit steady on rock target being drilled for subsurface sample. Credit: NASA/JPL

Anderson and his two SSS colleagues will have about 12 hr. to compare the rover images of the tailings with pictures taken when doing the same type drilling on the California rock samples in the JPL altitude chamber.

Based on what they see in the Earth and Mars tailings, the SSS team will either tell the engineering team that it is "Go" for actual drilling, "No Go" for drilling, or "needs more information before deciding either way," said Anderson.

Once they give permission, the plan now is to drill and deliver the initial sample to CheMin and also maybe SAM at the same time. But the rover engineering team is evaluating whether there will be enough time for a delivery to both on the same command cycle. If not, SAM will get its sample a day later.

It is likely the CheMin mineralogical data will be studied before SAM begins its own processing, "to avoid any surprises," before putting the powder into the intricate workings of the highly complex Goddard instrument, Anderson said. "Mars is the land of surprises," he added.

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