DART vs Dimorphos
On the first planetary defense
test mission from planet Earth,
the DART spacecraft captured this close-up on 26 September 2022,
three seconds before
slamming into the
surface of asteroid moonlet Dimorphos.
The spacecraft's outline with two long solar panels
is traced at its projected
point of impact between two boulders.
The larger boulder is about 6.5 meters across.
While the DART
(Double Asteroid Redirection Test)
spacecraft had a mass of some 570 kilograms,
the estimated mass of Dimorphos,
the smaller member of a near-Earth binary asteroid system,
was about 5 billion kilograms.
The direct kinetic impact of the spacecraft measurably
altered the speed of Dimorphos by a fraction of a percent,
reducing its 12 hour
orbital period around its
larger companion
asteroid 65803 Didymos
by about 33 minutes.
Beyond successfully demonstrating
a technique to change
an asteroid's orbit that can prevent future asteroid
strikes on planet Earth,
the planetary-scale impact experiment
has given the
150-meter-sized Dimorphos a
comet-like tail of material.