快猫短视频

THE small asteroid visited by NASA鈥檚 Deep Space 1 probe on 29 July appears to
be a chip off one of the largest and best-known asteroids: Vesta, which is 525
kilometres across.

Although Deep Space 1鈥檚 cameras were pointing the wrong way when the craft
zoomed by asteroid Braille
(快猫短视频, 7 August, p 13), it did record an
image from 14 000 kilometres away some 15 minutes later. The spectrum of light
given off by the asteroid suggests it has the same composition as Vesta.

Vesta has a shallow crater with a diameter of 460 kilometres around its South
Pole, indicating that it lost a sizeable chunk of rock from its surface after a
collision. 鈥淚t鈥檚 a good conjecture that Braille came from the hole,鈥� says Bonnie
Buratti, of the Jet Propulsion Laboratory in Pasadena. If so, Braille has been
thrown right out of its former orbit: Vesta orbits between Mars and Jupiter, but
Braille comes within 45 million kilometres of the Earth.

Deep Space 1鈥檚 snapshot suggests that Braille is between 1 and 2 kilometres
across, and consists of three distinct lobes. However, Rick Binzel of the
Massachusetts Institute of Technology warns that shadows can fool the eye. 鈥淏ut
it certainly looks like a pair of lobes,鈥� he says.