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Skywatch: Bringing space down to earth

Skywatch: Bringing space down to earth

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If you haven’t already, take a minute to google the OSIRIS-REx spacecraft’s touch-and-go sampling of the carbonaceous, near-earth asteroid (101955) Bennu, on October 20. The dramatic video provides a front-row seat to a brand of science atypical in our study of the universe.

Unlike most other sciences, astronomy rarely enjoys the luxury of directly sampling the objects of study. Roughly 100 tons of meteorites comprise most extraterrestrial material on Earth, with 842 pounds of rocks collected by six Apollo moon landings coming in a distant second.

Among the meteorites are exceedingly rare bits of known asteroids, the moon, and Mars, presumably blasted off those bodies long ago by violent impacts, ultimately plummeting to earth.

Despite Venus’s and Mercury’s proximity, we know of no meteorites that definitely originate from either, likely because of the difficulty for impact ejecta to escape Venus’s thick atmosphere and the sun’s deep gravitational well.

The Genesis probe, despite its crash-landing due to re-entry parachute failure, returned solar wind atoms and molecules from outside earth’s orbit in 2004.

The Stardust spacecraft collected both interstellar grains and bits of Comet Wild 2, dropped off on earth in 2006 and still being inventoried and studied.

Japan’s Hayabusa probe, despite numerous technical glitches, secured a few micrograms of dust plucked from the stony asteroid (25143) Itokawa in 2010.

Its successor, Hayabusa 2, collected a sample of the carbonaceous asteroid (162173) Ryugu in 2018, due to arrive early next month.

OSIRIS-REx got so much material from Bennu that it overfilled its collection chamber, now secured for return in 2023.

Finally, the Perseverance rover, launched in July, will cache samples of Mars on the Red Planet’s surface by 2023, although there are no definite plans yet for retrieving them.

Next column: A lunar eclipse for aficionados only.

Chris Anderson manages the College of Southern Idaho’s Centennial Observatory in Twin Falls. He can be reached at 732-6663 or


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