The origin of belt/zone contrasts in the atmosphere of Jupiter and their correlation with 5-micron opacity

Icarus 149 (2001) 397-415

Authors:

PG Irwin, A.L. Weir, F.W. Taylor, S.B. Calcutt

MUSE: Looking for life on Earth

ESA SP PUBL 496 (2001) 389-391

Authors:

AJ Penny, GR Davis, SB Calcutt, JR Drummond, DA Naylor, S Seager

Abstract:

Future missions to measure the mid-infrared spectra of extrasolar planets will obtain spectra spatially integrated over the visible hemisphere of the planet. Interpretation of these spectra will be difficult because they will depend on several imponderable factors; the axial inclination of the planet to the line of sight, the illumination of the planet by its parent star, and the planets' season and climatic state. The spectra will also contain variable components due to changing clouds, planetary rotation and the presence of large satellites. In order to interpret better such spectra, and to constrain the design of missions to measure them, a study is underway of a dedicated mission to take spectra of the spatially-unresolved Earth and to quantify the dependence of the spectrum on these variables.

The origin of belt/zone contrasts in the atmosphere of Jupiter and their correlation with 5-μm opacity

ICARUS 149:2 (2001) 397-415

Authors:

PGJ Irwin, AL Weir, FW Taylor, SB Calcutt, RW Carlson

Proximate humid and dry regions in Jupiter's atmosphere indicate complex local meteorology

Nature 405:6783 (2000) 158-160

Authors:

M Roos-Serote, AR Vasavada, L Kamp, P Drossart, P Irwin, C Nixon, RW Carlson

Abstract:

Models of Jupiter's formation and structure predict that its atmosphere is enriched in oxygen, relative to the Sun, and that consequently water clouds should be present globally near the 5-bar pressure level. Past attempts to confirm these predictions have led to contradictory results; in particular, the Galileo probe revealed a very dry atmosphere at the entry site, with no significant clouds at depths exceeding the 2-bar level. Although the entry site was known to be relatively cloud-free, the contrast between the observed local dryness and the expected global wetness was surprising. Here we analyse near-infrared (around 5 μm) observations of Jupiter, a spectral region that can reveal the water vapour abundance and vertical cloud structure in the troposphere. We find that humid and extremely dry regions exist in close proximity, and that some humid regions are spatially correlated with bright convective clouds extending from the deep water clouds to the visible atmosphere.

Standardisation of 210Pb

Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine 52:3 (2000) 381-385

Authors:

DH Woods, NE Bowles, SM Jerome, de Lavison P, S Lineham, JL Makepeace, AP Woodman, MJ Woods

Abstract:

The standardisation of 210Pb is complicated by the presence of the daughters, 210Bi and 210Po. In addition, the low energies of the beta emissions from 210Pb make it difficult to obtain high detection efficiencies in an atmospheric proportional counter and hence produce the need for large extrapolations with consequential large uncertainties when extrapolating to unit efficiency with the conventional 4pi(PC)-gamma-coincidence technique. In order to produce a reliable standardisation, it is necessary to remove the daughter products. A solution of 210Pb was therefore chemically separated from its daughters and then standardised using the conventional 4pi(LS)-gamma-coincidence technique. The low energy (46 keV) and low emission probability (4%) of the associated photon emissions effectively rules out the possibility of using ionisation chambers as secondary standard transfer instruments for this nuclide. A germanium spectrometer therefore was calibrated for this purpose using 241Am as a normalising agent. The results of this work are presented together with an analysis of the standardisation uncertainties that can be achieved in practice.