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First comet sample returned
Encountering the comet Wild 2 {below) in early
2004, the Stardust spacecraft swept up tiny
samples of cometary dust in an aerogel collector
(above) and returned the material to Earth on
15 Jan 2006. Its ongoing analysis is providing
insights into the chemical make-up of this icy,
primordial body.
On 4 Jul 2005, a 350-kg (770-lb) copper "bullet"
from NASA's Deep Impact craft hit comet Tempel 1
at 10.3 km/s (6.4 mils). The impact - equivalent to
that of 4.7 tonnes (10,360 I b) of TNT - created a
crater 100 m (330 ft) wide and 30 m (1 00 ft) deep.
lnCIUCieO the toxic gas
cyanogen. Needless
panic-buying of gas
masks, "anti-comet
umbrellas" and "anticomet
pills" followed.
Ta il end: what happens to comets?
The "death" of a comet can come about in a variety
of different ways. Not all comets are tied to an orbit
Closest comet flyby by
a spacecraft: Giotto flew
around the Sun, and some of them simply fly out
within 200 km of Griggof
the Solar System. Each time a comet passes
Skjellerup on 10 Jul 1992.
the Sun, it loses samples of dust and ice; if all of
Most comet tails met by
the ice is lost, the comet can become an inactive,
a spacecraft: Ulysses flew
through the tails of Hyakutake
asteroid-like structure. Alternatively, complete loss
(1996), McNaught-Hartley
of ice can result in the comet breaking up into dust
(2004) and McNaught (2007).
clouds. Finally, comets can meet a violent end when
Most comets discovered
their orbit results in them crashing into a moon or planet.
by a spacecraft: The SOHO
(Solar and Heliospheric
Our own Moon (right) is pockmarked with impact craters
Observatory) had discovered
caused by comets and asteroids crashing into its surface.
2,574 comets by Dec 2013.
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