Space impacts – a brief history
The Hera mission is the latest in a line of impact missions launched from Earth
Collisions have been a driver of Solar System history, and humans have added to their number. Apollo lunar modules and Saturn V third stages were collided with the Moon to trigger artificial ‘moonquakes’, which revealed valuable information about the Moon’s interior structure.
In 2005 NASA’s Deep Impact collided with the comet Tempel 1 to uncover subsurface material. The large dust plume meant the crater couldn’t be imaged at the time and a 2011 flyby by the Stardust mission sent back unimpressive results.
More dramatic was NASA’s 2009 LCROSS mission, which slammed a Centaur upper stage at 2.5 km/s into Cabeus crater near the Moon’s south pole. A ‘shepherd’ spacecraft flew through the impact plume, sniffing out water ice and carbon dioxide
– of potential use to future colonists.
Last year, Japan’s Hayabusa2 shot a copper projectile into the 900m diameter asteroid Ryugu at 2 km/s, resulting in a crater of 20m across.
The DART collision will strike an asteroid five times smaller than Ryugu with a spacecraft more than 200 times larger than Hayabusa2’s 2kg projectile, moving three times faster. Its impact should deliver sufficient energy to achieve the first asteroid deflection experiment for planetary defence.