Rylo-7

Rylo-7 was a rogue asteroid which narrowly missed colliding with Mars and instead became the Earth's second moon.

Discovery
The discovery of the asteroid was first announced by astronomer Winston Rylo on 30 November 2142 at his California Particle-Based Telescope. He revealed that the asteroid, measuring more than 100 kilometres in length, had left the asteroid belt near Jupiter and had begun to drift toward Mars.

Monitoring
Scientists saw no immediate danger, but continued to monitor the asteroid over coming months. By 10 December 2142, it was calculated that Rylo-7 would intersect the orbit of Mars in about nine months' time, but it was impossible to estimate how close it would come to the Red planet.

On 20 January 2143, Dr. Kristeen Ballard reported that the asteroid had changed course and increased its speed, and was expected to reach Mars earlier. The reasons for the change in velocity and direction were unclear.

By 5 March 2143, Winston Rylo predicted that the asteroid would reach Mars in about six months, but he continued to see little chance of a collision with the planet. However, in an update a fortnight later, he revealed that Rylo-7 was now 40 million miles from Mars, and if it maintained its present course and speed, it was possible that it could be captured by Mars' gravitational field in just over four months, becoming another permanent moon.