TY - JOUR
T1 - Cometary delivery of biogenic elements to Europa
AU - Pierazzo, E.
AU - Chyba, C. F.
N1 - Funding Information:
This work was supported by the NASA Exobiology program and a Presidential Early Career Award for Scientists and Engineers. We thank C. McKay and an anonymous reviewer for their helpful comments on the manuscript.
PY - 2002
Y1 - 2002
N2 - Jupiter's moon Europa may harbor an ocean beneath its ice cover, but the composition of that ocean and the overlying ice is nearly entirely unknown. Regardless of uncertainties in models for Europa's formation, we estimate lower limits for Europa's inventory of biogenic elements (such as C, N, O, and P) by investigating the contribution to the inventory of impact events over Europa's geologic history. A series of high-resolution hydrocode simulations were carried out over a range of comet densities (1.1, 0.8, and 0.6 g/cm3, corresponding to porosities between 0 and 45%) and impact velocities (16, 21.5, 26.5, and 30.5 km/s). We found that at typical impact velocities on Europa most impactor material reaches escape velocity, and it is assumed to be lost from Europa. For a nonporous comet, some fraction (20% or higher) of the projectile is retained by Europa even at the highest impact velocity modeled, 30.5 km/s. For porous comets, however, a significant fraction of the projectile (above 25%) is retained only for the lowest impact velocity modeled, 16 km/s. Integrated over solar system history, this suggests that 1 to 10 Gt of carbon could have been successfully delivered to Europa's surface by impacts of large comets (around 1 km in diameter). This is a few times more carbon than is contained in the procaryotic biomass of the upper 200 meters of the Earth's oceans, but about 2 orders of magnitude less if the whole depth of the oceans is considered. Therefore, regardless of its initial formation conditions, Europa should have a substantial inventory of "biogenic" elements, with implications for the chemistry of its oceans, ice cover, and the possibility of life.
AB - Jupiter's moon Europa may harbor an ocean beneath its ice cover, but the composition of that ocean and the overlying ice is nearly entirely unknown. Regardless of uncertainties in models for Europa's formation, we estimate lower limits for Europa's inventory of biogenic elements (such as C, N, O, and P) by investigating the contribution to the inventory of impact events over Europa's geologic history. A series of high-resolution hydrocode simulations were carried out over a range of comet densities (1.1, 0.8, and 0.6 g/cm3, corresponding to porosities between 0 and 45%) and impact velocities (16, 21.5, 26.5, and 30.5 km/s). We found that at typical impact velocities on Europa most impactor material reaches escape velocity, and it is assumed to be lost from Europa. For a nonporous comet, some fraction (20% or higher) of the projectile is retained by Europa even at the highest impact velocity modeled, 30.5 km/s. For porous comets, however, a significant fraction of the projectile (above 25%) is retained only for the lowest impact velocity modeled, 16 km/s. Integrated over solar system history, this suggests that 1 to 10 Gt of carbon could have been successfully delivered to Europa's surface by impacts of large comets (around 1 km in diameter). This is a few times more carbon than is contained in the procaryotic biomass of the upper 200 meters of the Earth's oceans, but about 2 orders of magnitude less if the whole depth of the oceans is considered. Therefore, regardless of its initial formation conditions, Europa should have a substantial inventory of "biogenic" elements, with implications for the chemistry of its oceans, ice cover, and the possibility of life.
KW - Comets
KW - Europa
KW - Exobiology
KW - Impact processes
KW - Prebiotic environments
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U2 - 10.1006/icar.2001.6812
DO - 10.1006/icar.2001.6812
M3 - Article
AN - SCOPUS:0036080931
SN - 0019-1035
VL - 157
SP - 120
EP - 127
JO - Icarus
JF - Icarus
IS - 1
ER -