Watch out Yosemite — the moon has its own impressive rock display.
When Apollo astronauts landed on the moon in the 1960s and 1970s, they granite.html” title=”The Moon's Surface Probably Conceals Granite”>encountered vistas dominated by basalt. The igneous rock is run-of-the-mill stuff on both the moon and our planet, says Matthew Siegler, a planetary scientist at the Planetary Science Institute in Tucson. “Everything starts as basalt.”
But over time, with enough heat and pressure, basalt can melt and morph into more durable granite. Plate tectonics and water, both mainstays on Earth, often help facilitate that transformation: Tectonic forces can help drag rocks down deep, where it’s hotter, and water, acting like a salt, helps rocks melt at lower temperatures (SN: 1/13/21).
Because the moon has no plate tectonics and very little water, finding copious amounts of granite there would be unexpected, Siegler says. Indeed, out of the roughly 380 kilograms of moon rocks (about the heft of a large bear) brought back to Earth by Apollo astronauts, just a handful of millimeter-sized pieces are granite (SN: 7/15/19). “That’s our whole inventory,” Siegler says.
2023-07-19 08:00:00
Source from www.sciencenews.org