Working Papers Astronomy and Astrophysics Panel Reports (1991) / Chapter Skim
Currently Skimming:
Planetary Astronomy
Planetary Astronomy
Pages 235-256
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 235... ...
Identification of the composition of the surfaces of the satellites of the outer planets, including water ice (frost) on many satellites, sulfur dioxide and hydrogen sulfide on lo, and methane and nitrogen gas on Triton.
|
From page 236... ...
In the 1970's, NASA built the 3-meter national Infrared Telescope Facility (IRE;) in Hawaii and contributed to the development and operation of the Arecibo planetary radar facility in Puerto Rico.
|
From page 237... ...
These disks may be the equivalent of the solar nebula out of which our own planetary system formed some 4.5 billion years ago. An important step toward placing the origin and evolution of the solar system in the context of other planetary systems was the discovery by the Infrared Astronomy Satellite (IRAS)
|
From page 238... ...
Many of the most important advances in planetary studies during the '70s and '80s involved the identification of ices and organic materials on many objects, ranging from the moons of Mars to the comets of the distant Oort cloud. These objects preserve relatively pristine material from the time that the solar system formed from the primordial solar nebula.
|
From page 239... ...
Spectrophotometric studies have revealed a variety of mineralogical classes, interpreted as representing various degrees of metamorphic and aqueous modifications of original primitive organic material. We have established further that composition is correlated with distance from the Sun, and therefore that the current asteroid population preserves information on the spatial variation of conditions in the solar nebula.
|
From page 240... ...
stellar occultation observations for determination of Pluto's atmospheric structure. Learning how the observed quantities change as a function of solar distance will be a further diagnostic for inferring more about the system.
|
From page 241... ...
Even when a spacecraft encounter has yielded a much more detailed study of a target at one particular epoch, these Earth-based studies must be made to relate the spacecraft data to events on the longer time scales characteristic of planetary seasonal changes or the 11-year solar cycle. Dynamics of Planetary Atmospheres The Voyager encounters with Jupiter, Saturn, Uranus, and Neptune have revealed great diversity in the dynamics and circulation patterns of the atmospheres of the giant planets.
|
From page 242... ...
The unknown winds on both planets can be observed by doppler spectroscopy utilizing rotational translations of the carbon monoxide line at millimeter wavelengths. Planetary Rings and Ring Dynanucs Observations of occultations of stars by solar objects will continue to be a major tool of planetary science.
|
From page 243... ...
The volcanoes on lo channel the release of internal heat through a limited number of vents or hot spots that are observable from Earn in the thermal infrared region of the spectrum. The emission spectrum of the thermal regions is clearly apparent during eclipses, but even when not eclipsed the hot spots are detected, and with spatial resolutions of 0.1 to 0.3 arcsec individual volcanoes can be identified and studied in detail.
|
From page 244... ...
Spectroscopy with comparable spatial resolution should isolate characteristic mineralogy, and permit geologic interpretation of the regional internal and surface processes which have been active throughout the planet's history. Examination of photographs of the surface of Mars leads to the inescapable conclusion that there once must have been large quantities of fluid on the surface.
|
From page 245... ...
at the IRTF and a better understanding of the seeing (degree of atmospheric interferences at Mauna Kea, which shows that images as small as 0.2 arcsec can be obtained in the near infrared region of the spectrum. A further bonus of this wavelength region is that the jovian planets have deep methane absorption bands, so that most, if not all, of the small satellites discovered by Voyager can now be studied from Earth.
|
From page 246... ...
SIRTF will obtain spectra of comets, asteroids, and planetary satellites in the infrared region, where diagnostic molecular bands reveal the chemistry of these varied objects. The ices that condensed in the collapsing solar nebula further than 5 AU from the Sun and that are now locked in the comets and satellites carry the chemical history of the nebula in the zones where the outer planets formed.
|
From page 247... ...
Occultations of stars provide a powerful tool for the study of planetary atmospheres and rings. The altitudes of a planetary atmosphere probed by an Earthbased stellar occultation lie in the gap between spacecraft radio occultations and ultraviolet stellar and solar occultations.
|
From page 248... ...
Current ground-based studies using doppler spectroscopy and astrometry have the capability to detect Jupiter-mass planets orbiting the nearest stars. An improved astrometric telescope at an excellent site (discussed below, on page 17)
|
From page 249... ...
For example, ultraviolet spectroscopy of comet Kopff will directly support the in situ spacecraft exploration of this comet in the first decade of the next century. It could also be employed to study the long-term evolution of phenomena in planetary atmospheres (e.g.
|
From page 250... ...
Such a facility would be an enormous improvement over any currently existing telescope, and it would provide the focus for much ground-based research in planetary astronomy and solar system formation. Although several other 8-meter optical/infrared telescopes are Planned or under construction, none of these is optimized for the infrared region of the spectrum.
|
From page 251... ...
One option is to optimize for infrared work one or more of the two 8-meter telescopes planned to be constructed by the National Optical Astronomy Observatories with support from He NSF. An alternative is to consider an 8-meter-class telescope as a possible replacement for the NASA-supported 3-meter infrared telescope FIRM built on Mauna Kea in the 1970's.
|
From page 252... ...
. An additional task for an astrometric telescope that would be important for planetary astronomy is its use for the accurate prediction of stellar occultations by bodies subtending small angular diameters, such as Triton, Charon, and Pluto.
|
From page 253... ...
Major Space-based 1. Space Infrared Telescope Facility (SIRED Moderate Space-based: 1.
|
From page 254... ...
However, these surveys must be designed so as not to exclude moving or variable targets. It is important that planetary astronomers participate in planning future survey programs, and that these programs be operated in such a way that important data on planetary sources are not discarded.
|
From page 256... ...
SCHREIER, Space Telescope Science Institute JOHN R STAUFFER, NASA Ames Research Center GERALD JAY SUSSMAN, The MIT Artificial Intelligence Laboratory JOSEPH H
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.