11.26 - Understand the advantages and disadvantages of the major types of space probe:
c) impactor

11.27 - Know an example of each type of space probe, including target body and major discoveries, including:
c) impactor – Deep Impact (comet Tempel 1)

An impactor is set to hit a body and usually an accompanying probe will analyse the effect of its impact.


  • An impactor will disturb materials allowing us to find what it is composed of in a way that an orbiter or lander could not.
  • We can see sometime see observations of the impactor as it is en route to its target.


  • An observation craft usually delivers and monitors the impact event. Two probes are more expensive.
  • Not knowing the results of the size of events can cause mistakes in the readings of the monitoring craft. Deep Impact was thought to be too close to the explosion to take the most efficient readings. LCROSS was too far away.

Deep Impact

The impactor was the size of a fridge, had its own set of rockets to move into position and hit the comet at over 35,000km.
Results showed the material was fine - more like 'talcum powder than sand' and compositon of materials ejected were analysed. Deep Impact was unable to take quality images of the crater that was formed but a later probe Stardust recorded this.


Other Missions

Using impactors has been an early method of finding out about other bodies. The Apollo porgram used multiple impactors on the Moon before sending Astronauts.

LCROSS was launched in 2009 and aimed an impactor called Centaur to a permantently shadowed crater with the aim of disturbing and detecting water molecules in the impact plume as LCROSS moved through the plume. This it did and found water evidence.