Mars Rover Finds Ancient Life-Supporting Lakebed
This mosaic of images from Curiosity's Mast Camera (Mastcam) shows geological members of the Yellowknife Bay formation, and the sites where Curiosity drilled into the lowest-lying member, called Sheepbed, at targets "John Klein" and "Cumberland."
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.
The site where NASA’s Mars rover Curiosity landed last year contains at least one lake that would have been perfectly suited for colonies of simple, rock-eating microbes found in caves and hydrothermal vents on Earth.
Analysis of mudstones in an area known as Yellowknife Bay, located inside the rover’s Gale Crater landing site, show that fresh water pooled on the surface for tens of thousands -- or even hundreds of thousands -- of years.
“The results show that the lake was definitely a habitable environment,” Curiosity lead scientist John Grotzinger, with the California Institute of Technology, told Discovery News.
The really big surprise, however, was that clays drilled out from inside two mudstones and analyzed by the rover are much younger than scientists expected, a finding that extends the window of time for when Mars may have been suitable for life.
“These numbers now overlap with the oldest rocks on Earth that contain evidence of a former biosphere on Earth,” Grotzinger said.
The rover explored Yellowknife Bay before heading toward a three-mile high mountain of layered sediments rising from the floor of Gale Crater known at Mount Sharp.
Curiosity landed in August 2012 to assess if Gale Crater had the right ingredients and environments to support ancient microbial life. Within six months, scientists had the answer to that question: Yes.
Now, in addition to characterizing specific potential habitats, scientists are coming up with a search strategy to determine which sites hold the most promise for finding organic carbon, a far more difficult and complex challenge and the focus of future studies at Mount Sharp.
“Habitability only requires that the chemicals and minerals in the rock preserve evidence of an ancient environment. To search for organic carbon you’re actually looking for particular material ... that is not really compatible with the present environment of Mars. To find something you need a guidebook, you need some rules,” Grotzinger said.
One of those rules involves how much radiation a rock has been exposed to. Mars today has only has a thin atmosphere and no protective magnetic field, so scientists have been thinking they will need to dig deep to find carbon-laced samples, or they will have to probe craters relatively recently excavated by an impact.
Analysis of the Yellowknife Bay rocks points to another path. Dating the ages of the rocks’ surfaces show they are as young as about 70 million years, the result of being sand-blasted by Martian winds.
“In the future, if we find a rock that looks like a place where organics were accumulating and if it looks like the chemistry would have been favorable for preservation ... we can now very deliberately manage the risk that the rock would have been cooking away in the presence of radiation for hundreds of millions of years by looking for these scarps, these miniature cliffs, and then drilling the rock and date it to see how long it’s been laying around,” Grotzinger said.
In related research, scientists found that the amount of radiation measured by Curiosity during its first year on the Martian surface is about 40 percent of what the rover experienced during its nine-month cruise.
Most of the reduction, as expected, is due to the planet’s body serving as a buffer, but scientists also found that solar activity is a key factor, said Cary Zeitlin at Southwest Research Institute.
Six papers on Curiosity’s new findings are published in this week’s journal Science and unveiled at the American Geophysical Union conference in San Francisco.