According to new research, some of the best places on Mars to look for valuable ores are volcanoes, lava flows and impact craters.
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 best places on Mars for valuable ores are volcanoes, lava flows and impact craters.
— Mars' different history, crust and atmosphere make it certain that minerals there will be different than those of Earth.
— Martian miners will not likely be sending much back to Earth.
Future Mars prospectors will likely find mineral riches in some unusual settings, say planetary scientists studying the different ways valuable metals might have been concentrated on the red planet.
On Earth, surface waters, ground waters and even chemicals left by living things play major roles in leaching, concentrating and depositing valuable metals and minerals like iron, gold, silver, nickel, copper and many more.
But on Mars there are no oceans or surface waters; no microorganisms either. What's more, the planet is so cold that even groundwater is frozen as permafrost and functions as little more than another mineral in the ground.
So where does a starving miner look on Mars for usable quantities of ore?
Try the volcanoes and impact craters, says planetary scientist Michael West of Australian National University in Canberra and the Mars Institute.
West is the lead author of a paper summing up what can and can't say about usable ores on Mars, which will appear in the March issue of the journal Planetary and Space Science. Among one of West's conclusions: Mars is no place to get rich.
The vast volcanic landscapes of Mars, for instance, are analogous to what geologists call the "Large Igneous Provinces" (LIPs) of Earth. These are areas where lots of lava poured out over the surface — as in, for example, Siberia, India and many parts of western North America.
Elements that are extracted from Earth's LIPs include nickel, copper, titanium, iron, platinum, palladium and chromium.
Mars' large volcanoes mountains themselves might also prove fruitful, says SETI planetary scientist Adrian Brown.
"We never know what we're going to find around the volcanic edifices," said Brown. "But they are covered with dust" and not ideal places to land rovers for exploration. So it might be a while before we ever find out.
Other potential mineral hot spots are the abundant large impact craters on Mars, said West. One reason is that craters offer up exposed rocks to prospect, which saves a lot of digging.
They are also places where there was a lot of heat which sometimes lasted for hundreds of thousands of years after the impact. That means any water frozen in the ground was turned to liquid and even steam, which can leach minerals and elements from local rocks and then deposit them in more concentrated forms in cracks (called veins of ore) and in hydrothermal vents.
On Earth vein ores rich in copper, zinc, lead and gold are found in the Sudbury impact structure in Canada. Other impact-related ores in the United States and Sweden have yielded silver, lead, zinc and barium, West said.
It's also important to remember that because of Mars' different history, some minerals found on Earth simply will not exist on Mars, said West's co-author Jonathan Clarke of Australian Center for Astrobiology at the University of New South Wales in Sydney, Australia.
"Mars has a different crust than Earth, and very different atmosphere" and so its minerals are going to be no less different.