The Micrometeoritic Purity of the Atmosphere and Early Earth’s Processes

Abstract

The basic time frame of EMMA is the formation time interval of the Earth, Δ(Earth) ~ 100 Myr. This value has been estimated from both the ¹²⁹I– ¹²⁹Xe radioactive chronometer (Pepin and Phinney, 1975; Staudacher and Allègre 1982) and modern theories about the formation of the Earth initiated by Wetherill (1994) –for a recent summary see Canup and Agnor (2000). In this scenario, the composition of the Earth’s atmosphere reported in Table 1 would give the average composition of about 1000 billions of billions of billions (e.g., ~10³⁰) of juvenile IDPs captured by the Earth after the formation of the Moon, and representing a total mass of material of ~5.10²⁴ g. Amazingly, this composition turns to be quite similar to that of an aliquot of about 500 AMMs with sizes of around 100.200 μm, amounting to a few milligrams of material, that we used to infer the composition of a “micrometeoritic” atmosphere.