— 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.