 |
| Titel |
The Aftermath of the 2009 Impact on Jupiter from Thermal-IR Spectroscopy |
| VerfasserIn |
Leigh Fletcher, Glenn Orton, Olivier Mousis, Imke de Pater, Heidi Hammel, Carey Lisse, Michelle Edwards, Agustín Sánchez-Lavega, Amy Simon-Miller, Padma Yanamandra-Fisher |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037168
|
|
|
|
|
|
| Zusammenfassung |
| The unexpected collision of an asteroidal or cometary body with Jupiter on July 19th 2009
was only the second observed impact event in the history of ground-based observations of the
giant planets. In the days that followed, the impact ejecta field was characterised by
multi-spectral observations from the mid-IR to the near-UV using a wide range
of ground-based and space-based observatories. Thermal-IR imaging from IRTF
/MIRSI on July 20th detected the warm impact scar at all wavelengths except near 7
μm (sensitive to stratospheric methane emission), indicating that the atmospheric
perturbation resulting from the impact was restricted to the lower stratosphere and upper
troposphere. These results were confirmed by Gemini-N/Michelle, Gemini-S/TReCS and
VLT/VISIR thermal observations in the following days, as the impact field elongated and
became sheared by Jupiter’s zonal jets. Enhanced Q-band (17-25 μm) emission was
attributed to elevated temperatures and stratospheric particulates, but enhanced N-band
emission (8-13 μm) could only be explained by significant quantities of ammonia
(NH3) gas exhumed from the tropospheric reservoir and emplaced into the warm
stratosphere.
Spatially resolved N-band spectra from Gemini-S/TReCS, with multiple observations
providing centre-to-limb variability of the enhanced emission, were used to derive 3D maps
of the enhanced temperatures and excavated NH3 distribution. We use these to estimate the
size and energy of the impactor and the mass of tropospheric air exhumed by the impact
shock and subsequent upwelling. High-resolution VLT/VISIR spectroscopic observations
taken at three epochs (July-November 2009) following the impact were used to track (a) the
rate of stratospheric NH3 depletion by photolysis and dynamic redistribution; and (b) the
radiative cooling timescale of the lower stratosphere. Imaging observations provide an
excellent temporal database to determine the expansion rate of the impact and ejecta
fields as they cooled. Finally, residual spectra from N-band retrievals are interpreted
as the signatures of material supplied to the Jovian atmosphere by the incoming
projectile, allowing us to constrain the possible composition and origin of the impacting
body.
* Fletcher is a Glasstone Science Fellow at the University of Oxford. We wish to
acknowledge the invaluable contributions of the support staff at IRTF, VLT and Gemini. |
|
|
|
|
|
|