> “Nearly four billion years ago, an asteroid or comet flew over the lunar south pole, brushed by the mountain summits of Malapert and Mouton, and hit the lunar surface,” Kring said. “The impact ejected high-energy streams of rock that carved two canyons … in less than 10 minutes.”
For comparison, it took 5 million to 6 million years for water to erode the landscape of Arizona to create the Grand Canyon.
Well yeah, it sounds perfectly reasonable that two wildly different mechanisms of producing a crack in the surface of a celestial body would also work on wildly different timescales. I mean, the crater itself (which is even bigger than the "canyons") also formed within 10 minutes or less, but that doesn't sound so spectacular, because all impact craters are formed this way.
From the Nature article[1], despite being prominent in the abstract it's almost a throwaway in the body:
> ... Moon’s Vallis Schrödinger and Vallis Planck were carved by streams of impacting rock in less than 10 min.
and earlier in the same article:
> Flight times of debris producing the 270 km-long main canyon are 4.9 to 15.0 min for Vallis Schrödinger over the entire range of potential ejection angles, with canyon-forming secondary impacts occurring within a 5 min interval. Flight times of debris producing the 280 km-long main canyon are 5.2 to 15.4 min for Vallis Planck over the entire range of potential ejection angles, with canyon-forming secondary impacts occurring within a 5 min interval.
I didn't dig all the way into how we get 10 minutes from 4.9-15 minutes. I was very interested in how this time was so confidently bounded. I'm guessing it's the graph that charts impact sizes, distances, and energies to assume flight travel time from a point of impact.
I'm also annoyed at the shift from "min" to "minutes" during the article. That just seems like really bad editing.
For comparison, it took 5 million to 6 million years for water to erode the landscape of Arizona to create the Grand Canyon.
Well yeah, it sounds perfectly reasonable that two wildly different mechanisms of producing a crack in the surface of a celestial body would also work on wildly different timescales. I mean, the crater itself (which is even bigger than the "canyons") also formed within 10 minutes or less, but that doesn't sound so spectacular, because all impact craters are formed this way.