THE SCHOOL OF SPACE ROCKS
ON 6 DECEMBER 2020, pieces of a near-Earth asteroid are scheduled to fall to Earth near Woomera, South Australia. Three years later, in September 2023, pieces of another near-Earth asteroid will land in the desert west of Salt Lake City, Utah.
In and of themselves, these events are nothing unusual. Chips from broken asteroids have been falling to Earth as meteorites since time immemorial. What makes these two different is that they are samples being returned by missions launched several years ago by Japan and the US, in a chase to bring pristine bits of near-Earth asteroids back to study in the world’s most sophisticated laboratories.
Hayabusa1’s 1500 tiny dust grains – less than a milligram of material overall – may be the most hard-won geological sample in the history of science.
To the extent it’s a race, the Japanese have long had a head start. In 2003, they launched Hayabusa1 (the name means falcon), which in 2005 rendezvoused with 25143 Itokawa, a 330-metre asteroid from which it intended to scoop up a few bits of sand and dust. (The numbers associated with asteroid names designate their order of discovery. The first, 1 Ceres, was spotted by astronomers in 1801.)
Hayabusa1 was plagued by problems. First, as it was on its way to Itokawa the largest solar flares in recent history damaged its solar panels, reducing the efficiency of its electrically powered ion engines enough to delay its arrival by three months. Then, two of the reaction wheels that controlled its orientation failed. Additional problems ensued as the wounded spacecraft repeatedly tried to touch down on the surface, where it was supposed to fire a high-velocity pellet at the substrate and scoop up the flying bits of rock (see Guns vs gas, page 81). Just as beleaguered Japanese scientists concluded that they might, perhaps, have managed to collect a few precious samples, they lost contact with the spacecraft for 46 days as it tumbled helplessly in space.
It was, basically, a case study in Murphy’s Law: if anything can go wrong, it will. And if anything else can also go wrong, so too will it. Which made it an utter triumph when, in 2010, Hayabusa1
