Mystery of Mars' Missing Methane Deepens
On sol 393 (Sept. 13) of Curiosity's mission, the rover snapped this image of a rocky outcrop called "Darwin" that the rover will study before continuing its rove to Mount Sharp (pictured in the distance).
Since NASA's Mars Science Laboratory (MSL) rover Curiosity landed on the red planet, each sol (a Martian "day") of the mission sees a flood of new photographs from Aeolis Palus -- the plain inside Gale Crater where Curiosity landed on Aug. 5. In September 2012, mission controllers sent the command for Curiosity to flip open the dust cap in front of the robotic arm-mounted Mars Hand Lens Imager (MAHLI). Until that point, the semi-transparent dust cap only allowed MAHLI to make out fuzzy shapes -- although it did a great job imaging Curiosity's "head" and it is also famous for capturing Curiosity's first color photograph. But since the true clarity of MAHLI has been unleashed, we've been treated to some of the most high-resolution views of the rover, Martian landscape and, most importantly, we've seen exactly what MAHLI was designed to do: Look closely at Mars rocks and dirt, assembling geological evidence of potential past habitability of Mars.
The Business End
Curiosity is armed with 17 cameras and MAHLI is designed to capture close-up photos of geological samples and formations as the rover explores. MAHLI was designed and built by Malin Space Science Systems and is analogous to a geologist's hand lens -- only a lot more sophisticated. Its high-resolution system can focus and magnify objects as small as 12.5 micrometers (that's smaller than the width of a human hair!). This photograph captured by the rover's Mastcam shows the MAHLI lens (with dust cap in place) in the center of the end of Curiosity's instrument-laden robotic arm.
To aid its studies, MAHLI is equipped with four LEDs to light up the imager's samples.
The first photograph to be returned from MAHLI without the dust cover in place was received on Sol 33 (Sept. 8) of Curiosity's mission. Shown here is a view of the ground immediately in front of the rover. Although this photo was a test, mission scientists were able to do a very preliminary study of the large "pebble" at the bottom of the picture: "Notice that the ground immediately around that pebble has less dust visible (more gravel exposed) than in other parts of the image. The presence of the pebble may have affected the wind in a way that preferentially removes dust from the surface around it," they wrote.
How Did Lincoln Help MAHLI?
On Sol 34 (Sept. 9), MAHLI was aimed at Curiosity's calibration target. This target is intended to color balance the instrument and provide a "standard" for mission scientists to refer to. The 1909 Lincoln penny was provided by MAHLI's principal investigatory Ken Edgett. Using a penny as a calibration target is a nod to geologists' tradition of placing a coin or some other object of known scale as a size reference in close-up photographs of rocks, says the MSL mission site.
Although MAHLI will be used to examine microscopic scales, it is showing its prowess at generating some spectacular high-definition views of the rover. Shown here is a mosaic of Curiosity's three left-side dusty wheels.
Hazard Avoidance Cameras
Hazard Avoidance Cameras, or Hazcams, have become "standard issue" for the last three rovers to land on Mars. Mounted on the front and back of rovers Opportunity, Spirit and Curiosity, these small cameras provide invaluable information about the terrain and potential hazards surrounding the rovers. These cameras are not scientific cameras -- they are engineering cameras. Shown here, MAHLI has imaged the four front Hazcams on Curiosity. Interestingly, it was these cameras who returned Curiosity's first dusty image after touch down in August.
Using the flexibility of the robotic arm, MAHLI was able to check the underside of Curiosity. As the camera can focus on objects from 0.8 inch (2.1 centimeters) to infinity, MAHLI has incredible versatility allowing mission controllers to focus on the very small features of Mars to checking the health of the rover to viewing the impressive vistas beyond.
In October 2012, the Internet was abuzz with speculation about a "mystery object" lying beneath the rover during digging operations at "Rocknest." Sadly, after studying the translucent object, mission scientists deduced that it wasn't anything native to the alien environment, it was actually a piece of plastic that had fallen from Curiosity. Yes, Curiosity is littering the red planet.
The MAHLI camera was very attentive while Curiosity dug trenches in the Mars soil at "Rocknest."
In early 2013, MAHLI snapped another curious photo. This time, after driving to a rocky outcrop at a location dubbed "Yellowknife," the camera picked out what appeared to be some kind of organic-looking object embedded in the rock. Nope, it's not a Mars "flower" -- more likely it's a concentration of minerals.
In what has become an iconic photo of Curiosity, MAHLI was commanded to capture dozens of high-resolution pictures of the rover. Like an "arms length" shot you may have in your Facebook profile, Curiosity did the same, composing a mosaic of pics taken with its outstretched robotic arm.
Curiosity Cleans Up!
The Mars rover isn't only a scientific superstar, it also has a talent for cleaning. This circular pattern on a Mars rock was brushed aside by Curiosity's Dust Removal Tool (DRT), helping the rover carry out analysis of the rock surface beneath the layer of dirt.
NASA’s Curiosity rover was sent to Mars to drill into ancient rocks and look for evidence that the planet most like Earth in the solar system had the chemistry and environments to support microbial life.
But the rover, which landed the Gale Crater impact basin in August 2012, also has been scouring the thin Martian atmosphere for another potential life sign -- methane. Since the gas also can be produced geologically, any findings promised a meaty debate.
That discussion can be shelved, perhaps permanently, new findings from a team of Curiosity scientists shows. The most extensive search yet for methane in Mars’ atmosphere has come up empty.
“It’s disappointing, of course. We would have liked to get there and found lots of methane and measure all the isotopes,” lead researcher Christopher Webster, with NASA’s Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News.
“These are the most sensitive measurements made. It will not be corrected later in time. I’m very confident our measurement is correct,” he added.
Which is not to say that earlier findings of methane plumes in the planet’s atmosphere, made by Mars orbiters and infrared telescopes on Earth, were wrong.
Rather, the measurements from Curiosity, taken over an eight-month period, add a new twist into an already intriguing mystery.
“The plumes were already hard to explain before they disappeared,” Webster said. “Suddenly, the whole interpretation of the earlier observations is stuck.”
On Earth, methane lasts 300 years in the atmosphere before it is broken down by ultraviolet rays from the sun. Taking into account Mars’ greater distance from the sun and reduced atmospheric pressure, a plume of methane measured in 2003 should have been an easy find for Curiosity’s tunable laser spectrometer.
The instrument shoots infrared beams at air samples and measures how much energy is absorbed at particular wavelengths, a process that reveals concentrations of methane, carbon dioxide, water vapor, and isotopic variations of these gases.
Planetary scientist Michael Mumma, a physicist at NASA’s Goddard Space Flight Center in Greenbelt, Md., who was among the first to detect methane in Mars’ atmosphere, said the new findings from the Curiosity Mars Science Laboratory means Mars has an unidentified mechanism for destroying methane, a process that occurs much faster than the 200 years or so that would be expected given the planet’s photochemistry.
“We think that if Mars Science Lab lasted long enough and made sufficient measurements at a regular cadence that it should, at some point, see methane, if indeed there is another release on the planet. So far, we and other investigators have reported releases at several sites, several times much larger than the value reported by MSL,” Mumma told Discovery News.
“If any of those releases are correct -- and we expect future ones to occur -- then some of that methane will make its way toward Gale Crater and MSL should in fact see an enhanced level,” Mumma said.
The research appears in this week’s Science.