We use ground-based telescopes to obtain near-IR (1 - 5 micrometre) imaging spectroscopy of the planets Venus and Mars. This is normally done by using a slit spectrometer and setting the telescope to scan or step the slit across the disk of the planet. This builds up a 3D data array which contains a spectrum for each point on the surface of the planet. From such data we can extract monochromatic images at any wavelength, or spectra for any region of the planet. The near-IR region includes absorption features from a range of atmospheric gases, emission from airglow features in the upper atmosphere, and absorption features from surface minerals.
Venus - In the case of Venus we normally observe the planet's night side. The IR spectrum shows a number of wavelength regions (or windows) in which thermal radiation from the hot lower atmosphere can be seen - the wavelengths outside these windows are absorbed by atmospheric gases such as CO2 or H2O. These windows were discovered by Australian astronomer David Allen in the 1980's. We can use these windows to study the structure of the lower atmosphere which is hard to probe in other ways. We can also study the content of the sulphuric acid clouds which occur at altitudes of 40-70km. We also see infrared airglow emission from molecular oxygen high in the atmosphere which is observed in the form of a strong feature at a wavelength of 1.27 micrometres. This airglow emission is highly variable and provides a probe of the dynamics of the upper atmopshere.
Mars - In the case of Mars we look at reflected light from the surface. This provides information on the surface mineral composition and on the atmosphere through which the light passes. Of particular interest is the search for alteration products such as hydrated clay minerals, carbonates and sulphates, which would provide evidence for the past presence of water. Our spectra also show features due to water and CO2 ice, and due to the absorption of atmospheric gases.
Instruments - The telescopes and
instruments
we use for this work include: GNIRS
and NIFS
on the 8m Gemini Telescopes (in
Chile
and Manua Kea, Hawaii) IRIS2
on the 3.9m Anglo-Australian
Telescope,
CASPIR
on the
2.3m ANU
Telescope
(both at Siding Spring, Australia), UIST
on the 3.8m United
Kingdom
Infrared Telescope, and SpeX
and CSHELL
on the 3m NASA Infrared
Telescope
Facility (both at Mauna Kea, Hawaii).
 |
 |
| United Kingdom Infrared Telescope, Mauna Kea, Hawaii - Photo: Nik Szymanek | IRIS2 mounted at the Cassegrain Focus of the AAT |
Publications:
Chamberlain et al.,
2013, Icarus, in press
Cotton et al., 2012, Icarus, 217,
570.
Bailey, 2009, Icarus, 201, 444.
Bailey et al., 2008, Planetary Space
Science, 56, 1385
Bailey, et al., 2008, Icarus,
197,
247.
Bailey et al., 2007, PASP, 119,
228
Chamberlain et al., 2006, 23, 119
Jeremy Bailey - 26 October 2012