Masters Theses

Date of Award

8-2015

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Joshua P. Emery

Committee Members

Jeff Moersch, Lawrence Taylor

Abstract

Near-Earth asteroids (NEAs) are not expected to have H2O [water] ice on their surfaces because a) most accreted dry and therefore never contained H2O, and b) their relatively high surface temperatures should drive rapid H2O ice sublimation. However, OH/H2O has been detected on other anhydrous inner solar system objects, including the Moon and Vesta. Possible sources for OH/H2O in the inner Solar System might include production via solar wind interactions, carbonaceous chondrite or cometary impact delivery, or native OH/H2O molecules bound to phyllosilicates. As these processes are active in near-Earth space, detectable levels of OH/H2O might also be present on NEAs. OH/H2O can be detected by its absorption feature at wavelengths near 3 microns using near-infrared (2 – 4 microns) spectroscopy from ground-based infrared telescopes. Analysis of the shape of the 3-micron feature, coupled with the observed NEA orbital parameters and albedos, can help distinguish between the possible sources of OH/H2O. I used the SpeX instrument on NASA’s Infrared Telescope Facility (IRTF) to measure spectra in from ~2 to 4 μm[microns]. The study presented here uses 13 observations for 8 NEAs: (443) Eros (two observations), (1036) Ganymed (four observations), (3122) Florence, (54789) 2001 MZ7, (96590) 1998 XB, (285944) 2001 RZ11, (214088) 2004 JN13, (357439) 2004 BL86. The objects are split into two spectral groups based on band depth: No feature or shallow feature (<10%). NEAs in the no feature group are 2004 BL86, 2001 MZ7, 2004 JN13, 2001 RZ11, 1998 XB, and one observation of Ganymed (6/10). Objects with a shallow feature are Eros (both observations), Florence, and three observations of Ganymed (6/4, 9/27 and 10/19). The objects with 3-micron absorptions all have a sharp feature which indicates OH present on their surfaces. I conclude that the 3-micron bands detected on Eros and Ganymed are due to solar wind implantation. The band depth on Florence, on the other hand, is more likely to be due to carbonaceous chondrite impacts. The presence of volatiles on bodies traditionally thought to be “dry” has many future scientific prospects and should lead to more observations in this region.

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