Terraforming Mars via Aerobraking an Asteroid

Abstract

Terraforming Mars is a tantalizing topic for the future of humanity. It has been estimated that an increase in temperature of about four degrees Kelvin would result in a runaway greenhouse effect on Mars, raising the temperature and atmospheric pressure on Mars to habitable conditions. One of the proposed methods for terraforming Mars involves impacting an asteroid to raise the temperature by four degrees Kelvin. There has been apprehension at this method, though, due to the destructive capabilities of asteroids. Michio Kaku proposes that we use the atmosphere to slow the impacting body before collision. Modeling this proposition as an aerobrake maneuver, we explore thermal energy delivered during aerobraking as a percentage of the total energy delivered to Mars. We used a Runge-Kutta 4th order method to model the aerobraking of an asteroid from the Martian gravitational sphere of influence to different initial aerobraking altitudes. With an asteroid matching the physical aspects of 99942 Apophis (density of about 2 cmg 3 , mass of 4 × 1010 kg), only about 46% of the energy delivered can be dissipated via aerobraking. However, a comet with a density similar to Halley’s Comet (about 0.6 cmg 3 ) and a much smaller mass than 99942 Apophis (about 5 × 108 kg) can achieve around 56% of total energy delivered as thermal energy from aerobraking. The mass of the asteroid ultimately determines how large of a temperature increase the aerobraking body delivers. An asteroid matching 99942 Apophis can deliver the necessary energy to raise the temperature by four degrees Kelvin whereas around twenty comets matching the density of Halley’s Comet with a mass of 5 × 108 kilograms would be needed to deliver the necessary energy.