Two Mars Rovers Search for Clues to Life
The shadows of two generations of Mars rover: Opportunity (left) and Curiosity.
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 Mars rover Curiosity isn't the only vehicle driving on the Red Planet this week. A long-lived sibling rover is closing in on what may be its most scientifically interesting target since arriving on Mars more than eight years ago.
The golf-cart sized Mars Exploration Rover Opportunity is expected to soon reach a patch of bedrock on the rim of Endeavour Crater, located on the opposite side of the planet from Curiosity's landing site. The rock is believe to contain clay minerals, which form in the presence of water.
Clays also are believed to exist in the lower layers of Mount Sharp, the three-mile high mound of sediment that rises from the floor of Gale Crater, where Curiosity touched down on Aug. 6.
The timing is ironic, and possibly fortuitous. Opportunity, along with its twin rover Spirit, were only designed for 90-day missions to determine if their landing sites showed signs of past water.
The answers from both were a resounding "yes," paving the way for the much better equipped and more robust Curiosity geochemistry robot, which just began a two-year quest to assess the planet's potential for microbial life.
"One way I like to think about it is that Opportunity is the field geologist doing the exploration type of stuff, and Curiosity is the geologist who then takes samples back to his lab to do more detailed analysis on them," planetary scientist Diana Blaney, with NASA's Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News.
The different missions grew out of different, but complementary science goals.
"When Spirit and Opportunity were built, we had places (on Mars) that we knew had had water, but we really didn't have any evidence for any place where water had been around doing chemistry on the surface for a long time.
"In that era the big questions were 'What is the history of water at these particular locations on Mars?'" Blaney said.
With its 10 science instruments and a two-year design life, Curiosity, which is about the size of a small car, is intended to address two difficult follow-on questions: whether Mars had ingredients besides water, such as organics, necessary for life and whether it had the means to preserve it.
"The missions inform each other to a limited extent," said Cornell University's Steve Squyres, the lead scientist on the Opportunity mission and a participating investigator on Curiosity's.
"Obviously, both (Opportunity and Curiosity) are on Mars and we're interested in similar scientific questions with both. But they're very different landing sites and Mars is so variable in its character from one place to another that you have to be very cautious about taking results from one site and applying them to another," Squyres told Discovery News.
Opportunity and Spirit, which succumbed to the harsh Martian environment two years ago, also weren't designed to travel nearly as far as Curiosity. Though Opportunity has racked up 22 miles on its odometer, scientists had to plan for a mission to be conducted within about 550 yards of its landing site.
"We didn't know what we were going to see on the ground," said Blaney, a deputy project scientist on the Opportunity and Spirit missions.
With Curiosity, she added, scientists wanted to go to the place they believe had the best chance for preserving a record of habitability in the rocks.
"When you start dealing with habitability and the potential for life, you raise the bar for what kind of measurements you have to make," Blaney said. "You need more capable instruments. You have to be a lot more careful with contamination. It's just a harder measurement to make."