Atmospheric entry heating of micrometeorites at Earth and Mars: Implications for the survival of organics

The atmospheric entry heating of micrometeorites (MMs) can significantly alter their pre‐existing mineralogy, texture, and organic material. The degree of heating depends predominantly on the gravity and atmospheric density of the planet on which they fall. For particles falling on Earth, the alteration can be significant, leading to the destruction of much of the pre‐entry organics; however, the weaker gravity and thinner atmosphere of Mars enhance the survival of MMs and increase the fraction of particles that preserve organic material. This paper investigates the entry heating of MMs on the Earth and Mars in order to examine the MM population on each planet and give insights into the survival of extraterrestrial organic material. The results show that particles reaching the surface of Mars experience a lower peak temperature compared to Earth and, therefore, experience less evaporative mass loss. Of the particles which reach the surface, 68.2% remain unmelted on Mars compared to only 22.8% on Earth. Due to evaporative mass loss, unmelted particles that reach the surface of Earth are restricted to sizes <70 μm whereas particles >475 μm survive unmelted on Mars. Approximately 10% of particles experience temperatures below ~800 K, that is, the sublimation temperature of refractory organics found in MMs. On Earth, this fraction is significantly lower with less than 1% expected to remain below this temperature. Lower peak temperatures coupled with the larger sizes of particles surviving without significant heating on Mars suggest a much higher fraction of organic material surviving to the Martian surface.