Hubble and Solar System Science

I. Neill Reid,


Observations of major and minor objects within the Solar System have formed a key part of Hubble’s program since its launch in 1990. Hubble’s unparalleled angular resolution, advanced spectroscopic and imaging instrumentation, and synoptical perspective are unique, invaluable assets for detailed investigations of planets and planetary phenomena. Everyone remembers the original “comet crash” into Jupiter by Comet Shoemaker-Levy 9 in 1994, which led to a series of iconic images and fully established the capabilities of the refurbished Hubble (Figure 1).  Since then, Hubble has been a consistent contributor to Solar System research through such diverse programs as monitoring auroral activity and atmospheric phenomena on the gas-giant planets, tracking the interactions of moons in the Jovian and Saturnian systems, investigating the binary frequency and chemical composition of trans-Neptunian objects and Main Belt asteroids, and probing the atmospheric characteristics of Mars and Venus.

In recent years, however, questions have arisen in the community about Hubble support for Solar System science and how that support may have changed over the years, qualitatively or quantitatively. One question is whether panel review can capture the range of expertise required for the evaluation of the full diversity of Solar System proposals. Another is whether the Call for Proposals might create new types of opportunity for the Solar System community to use Hubble. Indeed, when in 1985 the Institute director asked the Space Telescope Advisory Committee (STAC) for advice on “key projects,” the STAC’s Solar System subcommittee recommended a special way of doing business—the “planetary campaign”—rather than a specific science project. Under this scheme, the community would define a campaign of observations on a planet or another type of planetary target, to be coordinated with observations from various facilities, including planetary missions. Culturally, the planetary campaign resembles the way planetary missions, consisting of multiple investigations, are formulated. Comet Shoemaker-Levy 9 provided a brilliant instance of a planetary campaign (see sidebar). Another example is the Cycle 15 Large Hubble program devoted to studying Jupiter and Saturn during the International Heliophysical Year, 2007. Indeed, Hubble is currently contributing to a coordinated multi-observatory campaign to observe Comet ISON.