Cosmic curio: A little bit of Bennu
NEW DELHI : Half a century ago, astronauts brought back a total of a few hundred kilograms of rocks from the moon. It generated great excitement, because this was the first extraterrestrial material humans ever examined. There have been meteor strikes, of course.
But the moon rocks were the first such stuff that humans deliberately brought onto our planet. This week, another haul of extraterrestrial rocks landed on the earth. Not from the moon, though.
These were from an asteroid called Bennu that is, right now, motoring along about 82 million km from the earth. To put that in perspective, the moon is nearly 400,000 km away; the sun, about 150 million km. That 82 million km figure should flag another difference from the earlier haul: unlike the moon rocks, those from Bennu were not collected and brought home by humans.
Instead, it was a spacecraft named OSIRIS-REx. My last column reminded you of another meeting between spacecraft and asteroid. That was DART, which smashed into Dimorphos a year ago.
I assure you, OSIRIS-REx’s encounter with Bennu was far less violent. As I wrote in this space in 2020 (And yet she pirouettes, there above Bennu, https://t.ly/AuTVb), OSIRIS-REx spent two years finding its way to Bennu. Once there—it was about 300 million km distant at that point—it spent two more years flying alongside, and in orbit around Bennu.
For much of that time, through hundreds of orbits around the asteroid, it was examining Bennu, searching for the right spot on the surface from where to pick up asteroid-material. Eventually, the craft chose an area that Nasa called “Nightingale": a patch of something resembling sand, surrounded by rocks. OSIRIS-REx descended till a long extended arm with a cup at its end touched
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