A powerful verteron emitter on Mars built to redirect comets for terraforming, which the xenophobic Terra Prime movement captures in 2155 and turns into a weapon able to hit any target in the Solar system.
The verteron array is an installation on Mars seen in Demons and Terra Prime, the penultimate story of Star Trek: Enterprise. It was built to steer comets on to the Martian poles as part of the planet's terraforming, and its beam can reach anywhere in the system.
In 2155 John Frederick Paxton, leader of Terra Prime, flies the Orpheus mining facility from the Moon to Mars and takes control of the array. He fires a warning shot at the lunar surface and threatens to destroy Starfleet Command unless every alien leaves the system, using a cloned Vulcan-human child as his propaganda.
Archer leads a team to Mars in a shuttlepod hidden in the tail of a comet. They storm the facility, and the array's final shot is diverted so that it falls harmlessly into the sea near San Francisco.