Survival of organic compounds in ejecta from hypervelocity impacts on ice

Bowden, Stephen and Parnell, John and Burchell, Mark J. (2009) Survival of organic compounds in ejecta from hypervelocity impacts on ice. International Journal of Astrobiology, 8 (01). p. 19. ISSN 1473-5504. (doi:https://doi.org/10.1017/S147355040900442X) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Official URL
http://dx.doi.org/10.1017/S147355040900442X

Abstract

Hypervelocity impacts (HVIs) where organic-bearing ice constitutes the target material are important in several aspects of planetary and space science: (1) sampling of planetary surfaces using a hypervelocity projectile to impact the surface and eject surface materials for measurement or collection by a spacecraft; (2) the transfer of organic material between planetary bodies; and (3) providing energy for chemical processes involving surface materials. While small organic molecules (~6 carbon atoms), if present in surface materials, will likely be present in HVI-ejecta, uncertainty remains for larger organic molecules. It is the larger molecular weight compounds which could constitute direct evidence of life, and thus their survival within an HVI-ejecta plume is of key importance when evaluating strategies for life detection on icy bodies. It is not currently known what large organic molecules, and in what concentrations, may be present on icy bodies in the Solar System, but it is highly likely some will be more chemically stable during a HVI than others. Accordingly, in this study we examined a range of chemicals (β,β carotene, stearic acid and anthracene) with molecular weights between 178 and 536 daltons, and three different types of chemical structure. The compounds were solvated in a dimethylsulfoxide/water mixture and frozen. The frozen targets were impacted with steel spheres 1 and 1.5 mm in diameter at velocities of about 4.9 km s−1. Ice ejected during the impact was collected and underwent chemical analysis. The most labile compound (β,β carotene) was only detected (in small amounts) in the ejecta (and only that emitted at the lowest angles of ejection), although the other compounds were present in larger quantities and at a range of ejection angles. A concentration gradient was observed within the ejecta as a function of angle of ejection. This was not the same for both stearic acid and anthracene: the greatest concentrations of stearic acid were found at shallow angles of ejection whereas anthracene was most abundant at both intermediate and large angles of ejection, implying an inverted concentration gradient. These observations may indicate that organic compounds are variably altered and destroyed during a HVI with ice and that the ejecta plume does not sample the original materials equally at all angles of ejection. Future work is planned and will evaluate fractional survival for a greater range of compound types, impact materials and velocities.

Item Type: Article
Uncontrolled keywords: ejecta; hypervelocity; ice; organic; survival
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Q Science > QD Chemistry
Divisions: Faculties > Sciences > School of Physical Sciences
Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Mark Burchell
Date Deposited: 05 Dec 2013 12:57 UTC
Last Modified: 05 Jan 2015 13:47 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/37227 (The current URI for this page, for reference purposes)
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