Laboratory studies of isotope enriched ices relevant to the outer solar system.

摘要

Study of the ices on the surfaces of Mars, icy satellites, and Trans Neptunian Objects (TNOs) are limited by the dearth of laboratory spectra for comparison with telescope spectra. For example, CO ice has been detected on Pluto and Triton, and CO2 ice has been detected on the Martian polar caps and icy satellites around the giant planets. However, there are no systematic lab studies of 13CO and 13CO 2 enriched ice samples that would allow the calculation of 12 C/13C from telescope spectra of TNOs. Here we present laboratory absorption coefficients for CO in N2, 13CO in N2, CO2, and 13CO2. For CO in N2 and 13CO in N2, we were able to produce absorption coefficients for the 2υ1transitions from 60K down to 40K in 10K increments. For CO2 and 13CO 2 we produced absorption coefficients for the 2υ1+υ 3, υ1+2υ2+υ3, and 2υ 2+υ3 transitions from 190K down to 35K in 10K increments. We found the 12CO2 band centers and widths changed with temperature opening the possibility of using the centers and widths of bands in telescope spectra as means of measuring the temperature of TNOs. In addition, we found an interesting solid state physics effect, a broadening of the 12CO2 bands due to an increased 13 CO2 concentration. With these absorption coefficients in place all we need now are telescope spectra with sufficient signal to noise to measure 12C/13C in the icy surfaces of TNOs. Such measurements could constrain the level of physical and chemical processing of the icy grains, as well as indicate their location during the formation of the Solar System.