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Carolyn S. Shoemaker

Publications and source records attributed to Carolyn S. Shoemaker.

6 recordsLinked to original sources
USGS2012

Gravity survey of the Mount Toondina impact structure, South Australia

Gravity and seismic reflection data, together with geologic mapping, indicate that the Mount Toondina feature in South Australia is best interpreted as an eroded 4-km-diameter impact structure consisting of a ring structural depression surrounding a pronounced central uplift. Beds at the center of the structure within the central uplift have been raised as much as 200 m from depth and deformed by convergent flow. Seismic reflection data indicate that deformation extends to depths of only ≈800 m; at greater depths the reflectors are nearly flat lying, indicating little or no deformation. Gravity data show residual anomalies of +1.0 mGal coincident with the central uplift and a −0.5 Mgal low associated with the ring structural depression. Modeling of the gravity data indicates that relatively high-density material occurs within the central uplift, whereas the ring depression is filled with low-density material. The deformation at Mount Toondina is typical of a complex impact crater; the 4-km diameter is consistent with the expected threshold size for complex craters formed in weak to moderate strength sedimentary rocks.

South Australia↗
USGS1999

Ups and downs in planetary science

The field of planetary science as it developed during the lifetimes of Gene and Carolyn Shoemaker has sustained a period of exciting growth. Surveying the skies for planet-crossing asteroids and comets and studying the results of their impact upon the planets, especially the Earth, was for Gene and Carolyn an intense and satisfying quest for knowledge. It all started when Gene envisioned man going to the Moon, especially himself. After that, one thing led to another: the study of nuclear craters and a comparison with Meteor Crater, Arizona; the Apollo project and a succession of unmanned space missions to the inner and outer planets; an awareness of cratering throughout our solar system; the search for near-Earth asteroids and comets; a study of ancient craters in Australia; and the impact of Shoemaker-Levy 9 on Jupiter. The new paradigm of impact cratering as a cause for mass extinction and the opening of space for the development of new life forms have been causes to champion.

Annual Review of Earth and Planetary Sciences↗
USGS1995

The Hubble Space Telescope (HST) observing campaign on comet Shoemaker-Levy 9

The Hubble Space Telescope made systematic observations of the split comet P/Shoemaker-Levy 9 (SL9) (P designates a periodic comet) starting in July 1993 and continuing through mid-July 1994 when the fragments plunged into Jupiter's atmosphere. Deconvolutions of Wide Field Planetary Camera images indicate that the diameters of some fragments may have been as large as ∼2 to 4 kilometers, assuming a geometric albedo of 4 percent, but significantly smaller values (that is, < 1 kilometer) cannot be ruled out. Most of the fragments (or nuclei) were embedded in circularly symmetric inner comae from July 1993 until late June 1994, implying that there was continuous, but weak, cometary activity. At least a few nuclei fragmented into separate, condensed objects well after the breakup of the SL9 parent body, which argues against the hypothesis that the SL9 fragments were swarms of debris with no dominant, central bodies. Spectroscopic observations taken on 14 July 1994 showed an outburst in magnesium ion emission that was followed closely by a threefold increase in continuum emission, which may have been caused by the electrostatic charging and subsequent explosion of dust as the comet passed from interplanetary space into the jovian magnetosphere. No OH emission was detected, but the derived upper limit on the H 2 O production rate of ∼10 27 molecules per second does not necessarily imply that the object was water-poor.

Science↗
USGS1990

Asteroid and comet flux in the neighborhood of Earth

Approximately 90 Earth-crossing asteroids had been discovered through September 1989. Discovery is thought to be complete at absolute V magnitude (H) = 13.2 (the magnitude of the brightest known object, diameter ∼8.1 km), and about 6 percent complete at H = 17.7 (typical diameter about 1 km). The calculated mean probability of collision of Earth-crossing asteroids with Earth is (4.2 ± 1.7) × 10 −9 yr −1 . When multiplied by the estimated population of 1030 ± 470 at H = 17.7, this probability yields a collision rate of (4.3 ± 2.6) × 10 −6 yr −1 for asteroids larger than about 1 km in diameter. At H = 15.8, roughly equivalent to asteroid diameters more than 2 km, the estimated collision rate is ≈7 × 10 −7 yr −1 , and at 8-km diameter, the rate is ≈3 × 10 −9 yr −1 . Comet nuclei with diameters more than 2.5 km are estimated to strike the Earth at the rate of ≈ 10 −7 yr −1 ; comets larger than 10 km in diameter probably strike at a rate ≈10 −8 yr −1 . Impact of asteroids probably dominates the production of craters smaller than 30 km in diameter, whereas comet impact probably forms most craters larger than 50 km. The production rate for craters larger than 20 km in diameter, estimated from the astronomical evidence, is (4.9 ± 2.9) × 10 −15 km −2 yr −1 ; this rate is consistent with the cratering rate estimated by Grieve from the geologic record for the last 120 m.y.

Special Papers of the Geological Society of Americ↗
USGS1981

Survey for bright Mars-crossing asteroids

A new method of search for relatively bright Mars-crossing asteroids with the Palomar 46-cm Schmidt camera was initiated in 1980. Selected fields photographed with the 46-cm Schmidt were systematically reduced for all asteroids detected on the films. The 46-cm Schmidt fields have an effective diameter of 8 3/4 degrees. Kodak 11a-D film was exposed with a yellow plexiglass filter. The films were scanned with a specially designed stereomicroscope that permits recognition of asteroids by stereopsis. Stereoscopic pairs of films were exposed with a time separation of 30 minutes; over this interval the parallax in position relative to the background stars allows easy recognition of asteroids at distances ranging from near the Earth through the main belt. Optimum exposure for each film was found to be 10 minutes on the f/2 Schmidt.

Book chapter↗