Robert Novak    

Our group has been studying the atmosphere of Mars using CSHELL since
1997. Our first studies measured O2(1g) emissions (a tracer of
ozone), and HDO absorptions (then a proxy for water; we now measure
both HDO and H2O to measure D/H). By placing the spectrograph slit
across the planet N/S, we were able to obtain latitudinal maps of
these species; by stepping the slit across the planet, we obtained 2-D
maps over the entire range of Martian season. These initial
measurements led to further studies such as the geographic and diurnal
variation of the D/H ratio of Mars’ water and the identification of
methane on Mars. We began using ISHELL to study Mars in January,
2017. ISHELL with its higher spectral resolution (70000 vs 40000) and
its wider spectral range per image (~ 200 times larger) enhances the
quality of data taken with CSHELL, and enables a simultaneous search
for several related species (ad always CO2). With a larger spectral
grasp per image, more spectral lines per species can be measured
resulting in more precise measurements. Likewise, more molecules may
be measured simultaneously without changing the spectral setting of
the instrument. Our previous measurements of the D/H ratio required
two different spectral settings; both can now be measured in one
setting. When we measured methane, one setting using CSHELL gave us
one absorption line. An ISHELL setting give us an entire band plus
bands for related species such as ethane, propane, and butane. From
measuring these organic species simultaneously, we can test whether
the methane is of geological or biological origin. In summary, using
ISHELL to observe Mars’ atmosphere will provide enhanced measurements
of molecules that have been already measured and will enable
measurements of molecules that have not yet been detected on Mars,
especially those that have astrobiological significance. -R. Novak,
M. Mumma, G. Villanueva, S. FAggi