How can we build on Mars? A casual chat with a geologist led a University of Canterbury (UC) engineering academic and his team to spend years researching how to build on Mars. It all started with Associate Professor Allan Scott and Geology Professor Chris Oze (Occidental College) pondering what materials were available on Mars to make concrete or "Marscrete."

Earthly concrete is made with Portland cement, which is produced by heating limestone to drive off the CO₂. Cement, the main binder, is mixed with sand, stone, and water to create concrete.

But the pressing question is: What is available on Mars to bind the materials of Marscrete together?

"Unfortunately, on Mars there is not a lot of limestone so we are looking at alternative ways to find some sort of binder system," says Associate Professor Allan Scott.

A Christie's auction of rare meteorites Wednesday sold a rock from space that narrowly missed a German Shepherd when it smashed into his kennel in Costa Rica.

But the offer of the third-largest piece of Mars on Earth failed to make an impact at the auction house's annual sale of unusual meteorites.

The buyer paid $21,420 for the three-by-1.5 inch (eight-by-four centimeter) carbonaceous chondrite stone that landed in the garden of dog Roky's owner's home in Aguas Zarcas in April 2019.

The wood and tin doghouse itself, complete with a seven-inch hole marking where the meteorite punctured the roof, sold separately for $44,100, Christie's said.

That was much less than the pre-sale estimate of between $200,000 and $300,000.

A bidder paid $189,000 for a chunk of lunar rock that was discovered in Morocco in 2007, below pre-sale estimates of up to $300,000.

Another slice of the Moon—found in the Sahara desert in Mauritania—fetched $69,300 during the two-week online sale that ended Wednesday.