Laboratory emission spectra are measured at Arizona State University's Mars Space Flight Facility for comparison to remotely sensed data from Earth and Mars. Such emission spectroscopy using an interferometric spectrometer measures the energy of the sample, including reflected and emitted
background sources. The detector is uncooled at ambient temperature, which produces a very low signal when measuring the energy from a sample that has a temperature close to its own. In order to increase the energy difference between the sample and the detector, thereby increasing the signal
received by the detector, samples are typically heated to between 60 and 80 °C for several hours prior to measurement. While this method is acceptable for most rock and mineral samples, some hydrous minerals dehydrate quickly at low relative humidity and temperatures above room temperature.
This change is evident in both the physical appearance of the mineral and in the position and shape of its spectral absorptions. One solution to this problem is to heat samples to lower temperatures (e.g., 40 °C) for only a short time period. However, this approach results in a low signal
from the sample and does not always avoid dehydration. For this reason, we have developed a technique for measuring and calibrating emission spectra of hydrated minerals that involves cooling samples to well below the temperature of the detector, which avoids dehydration, while creating a
large delta temperature and a strong signal from the sample. Our method allows for accurate library spectra, with discrete, pronounced spectral features (high spectral contrast), of hydrated minerals that can be used for comparison to planetary surfaces.
Jet Propulsion Laboratory, Pasadena, California 91109 2:
Arizona State University, Tempe, Arizona 85287
Publication date: June 1, 2009
More about this publication?
The Society publishes the internationally recognized, peer reviewed journal, Applied Spectroscopy, which is available both in print and online. Subscriptions are included with membership or can be purchased by institutional or corporate organizations. Abstracts may be viewed free of charge. Previously published as Bulletin (Society for Applied Spectroscopy)