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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Spectrophotometry of Dust in Comet Hale-Bopp

Comets, such as Hale-Bopp (C/1995 O1), are frozen reservoirs of primitive solar nebula dust grains and ices. Analysis of the composition of cometary dust grains from infrared spectroscopic techniques permits an estimation of the types of organic and inorganic materials that constituted the early primitive solar nebula. In addition, the cometary bombardment of the Earth (approximately 3.5 Gy ago) supplied the water for the oceans and brought organic materials to Earth which may have been biogenic. Spectroscopic observations of comet Hale-Bopp suggest the possible presence of organic hydrocarbon species, silicate and olivine dust grains, and water ice. Spectroscopy near 3 microns obtained in Nov 1996 r=2.393 AU, delta=3.034 AU) shows a feature which we attribute to PAH emission. The spatial morphology of the 3.28 microns PAH feature is also presented. Optical and infrared spectrophotometric observations of comets convey valuable information about the spatial distribution and properties of dust and gas within the inner coma. In the optical and NIR shortward of 2 microns, the observed light is primarily scattered sunlight from the dust grains. At longer wavelengths, particularly in the 10 gm window, thermal emission from these grains dominates the radiation allowing an accurate estimate of grain sizes and chemical composition. Here we present an initial analysis of spectra taken with the NASA HIFOGS at 7-14 microns as part of a multiwavelength temporal study of the "comet of the century".

Witteborn, Fred C.↗
NASA NTRS1997

Collisional quenching of OH radio emission from comet Hale-Bopp

Observations of comets in the 18-cm OH transitions offer a means to probe gas production, kinematics, and OH excitation in comets. We present initial results of OH observations of comet Hale-Bopp obtained with the NRAO 43 m antenna located in Greenbank, WV. Maps of the emission provide strong constraints on the amount of quenching of the inversion of the OH ground state A-doublet in the coma. Analysis of the total radio OH flux and maps of its radial brightness distribution indicate a quenched region on the order of approximately 500,000 km during March and April 1997. This large value is generally consistent with previous observations of radio OH quenching in lower production rate comets when the high production rate of comet Hale-Bopp is considered.

NASA Discipline Exobiology↗
NASA NTRS1997

HCO+ in the coma of comet Hale-Bopp

Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO+ emission require a low abundance of HCO+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (Te). To set constraints on the formation of HCO+ in the coma, as well as the location and magnitude of the transition to higher Te, the data are compared with the results of ion-molecule chemistry models.

Non-NASA Center↗
NASA NTRS1996

The Detection of Water Ice in Comet Hale-Bopp

We present spectra of Comet Hale-Bopp (C/1995 01) covering the range 1.4-2.5 micron that were recorded when the comet was 7 AU from the Sun. These show I)road absorption features at 1.5 and 2.05 micron. We show that some, but not all, of this absorption could be matched by an intimate mixture of water ice and a low albedo material such as carbon on the nucleus. However, we recognize that it is more likely that the ice features are produced by scattering from icy grains in the coma. The absence of absorption at 1.65 micron suggests that this ice is probably in the amorphous state. An unidentified additional component may be required to account for the downward slope at the longwavelength end of the spectrum.

Davies, John K.↗
NASA NTRS1996

Activity of Comet Hale-Bopp (1995 01) Beyond 6 AU From the Sun

The physical evolution of comet Hale-Bopp is investigated along the preperihelic arc of its orbit at heliocentric distances larger than 6 AU. The comet's considerable intrinsic brightness and activity are explained by the existence of a relatively larg area on its nucleus surface that is a resevoir of both carbon monoxide and dust particulates. Three recuring dust emission events observed in August-October 1995 are studied in some detail.

Hale-Bopp evolution carbon monoxide dust particula↗
NASA NTRS1997

Interstellar and cometary ices: Molecular emission from comet Hale-Bopp

Observations of rotational translations of neutral molecules, radicals and ions in the comet Hale-Bopp are reported on. Sample spectra and maps of the emission for the J = 1 to 0 transition of HCN, the J = 2 to 1 transition of CS and the J = 1 to 0 transition of HCO+ are presented. While the emission from HCN is typically centered on the position of the nucleus and is symmetric, the emission from HCO+ exhibits multiple peaks, together with evidence for acceleration away from the nucleus.

Irvine, W. M.↗
NASA NTRS1997

Modelling two dust features in comet Hale-Bopp (1995 O1)

A Monte Carlo computer simulation code for generating synthetic images of dust features in comets is applied to comet Hale-Bopp to model the diurnal evolution of a bright jet and the appearance of nearly concentric halos.

comet-Hale-Bopp diurnal evolution of a dust jet du↗
NASA NTRS1997

The infrared spectrum of comet Hale-Bopp

The infrared spectroscopic observations of the comet C/1995 O1 (Hale-Bopp), in April and September-October 1996, are summarized. High resolution spectra were obtained with the long and short wavelength spectrometers of the Infrared Space Observatory (ISO). The results showed that the dust in this comet contains crystalline silicates. The dust of Hale-Bopp is rather similar to that observed in the circumstellar disks of Vega-type stars.

Crovisier, J.↗
NASA NTRS1996

(abstract) Spectra of Comet Hale-Bopp

The spectra of Hale-Bopp were acquired in mid-1996 at R > 3.5 AU. Strong silicate emission is present in all the spectra. The shape of the feature is very similar to that seen in comet P/Halley. This is the first time that a strong silicate feature has been detected in a comet beyond 2 AU.

comet silicate Hale-Bopp spectra↗
NASA NTRS1997

The HNC/HCN ratio in comets

The abundance ratio of the isomers HCN and HNC has been investigated in comet Hale-Bopp (C/1995 O1) through observations of the J = 4-3 rotational transitions of both species for heliocentric distances 0.93 < r < 3 AU, both pre- and post-perihelion. After correcting for the optical depth of the stronger HCN line, we find that the column density ratio of HNC/HCN in our telescope beam increases significantly as the comet approaches the Sun. We compare this behavior to that predicted from an ion-molecule chemical model and conclude that the HNC is produced in significant measure by chemical processes in the coma; i.e., for comet Hale-Bopp, HNC is not a parent molecule sublimating from the nucleus.

NASA Discipline Exobiology↗
NASA NTRS1997

STS-83 Postflight Presentation

The flight crew of the STS-83 mission, Cmdr James D. Halsell, Pilot Susan S. Still, Payload Cmdr. Janice E. Voss, Mission Specialists Donald Thomas and Michael Gernhardt, and Payload Specialists Roger Crouch and Greg Linteris, offer a video and still photo presentation of their journey. Included in the presentation are an introduction of the crew and a short briefing by Cmdr. Halsell, the launch and ascent narrated by Still, Spacelab Module narration by Voss, mission control narrated by Cmdr. Halsell, experiment narration by Thomas and Crouch. Also included are video views of the Baja Peninsula, Sinai Peninsula, pivot-point irrigation circles, Comet Hale-Bopp, and the cross-wind landing. The crew poses outside the shuttle for photos. Crew members discuss still photos taken during the mission, including shots of sunsets, the Grand Bahamas Island, Nile River, Baja Peninsula, Indis River of India, and Guadalupe Island.

Source record↗
NASA NTRS1997

STS-82 Mission Highlight Presentation

The STS-82 is the second in a series of planned service missions to the Hubble Space Telescope (HST). The flight crew of STS-82, Cmdr. Kenneth D. Bowersox, Pilot Scott J. Horowitz, Mission specialists, Mark C. Lee, Steven A. Hawley, Gregory J. Harbaugh, Steven L. Smith, and Joseph R. Tanner can be seen performing pre-launch activities preparing for the night launch. The crew meets the press for pre-launch photos before being transported to the launch pad. Several views can be seen of the final inspection team on the O level and the crew being readied in the 'white room'. Launch activities such as the oxygen vent hood retraction, liftoff, SRB separation, and personnel activities in the Houston Integrated Mission Control room are viewed. Subsequent footage is provided of the crew's activities during the HST rendezvous and docking, Extravehicular Activities (EVA's) preparation and EVA numbers 1, 3 and 5. During the first EVA the earth can be seen clearly in a reflection off of HST's offshroud during its 60th orbit crossing the equator. The HST deployment and views of the Hale-Bopp comet are clearly seen before Discovery's reentry and landing. After reentry a beautiful view of Discovery moving at 10,400 mph can be seen looking east from Mission Control. The ususal twin sonic boom precedes Discovery's touchdown on runway 15 at Kennedy Space Center. This second HST service mission orbited Earth 150 times and traveled 1.4 million miles.

Source record↗
NASA NTRS1997

STS-85 Day 08 Highlights

On this eighth day of the STS-85 mission, the flight crew, Cmdr. Curtis L. Brown, Jr., Pilot Kent V. Rominger, Payload Cmdr. N. Jan Davis (Ph.D.), Mission Specialists Robert L. Curbeam, Jr. and Stephen K. Robinson (Ph.D.), and Payload Specialist Bjarni V. Tryggvason entered the final portion of its flight. The new Mir 24 crew of Commander Anatoly Solovyev and Flight Engineer Pavel Vinogradov, who arrived on the station the same day Discovery was launched, bid farewell to Mir 23 Commander Vasily Tsibliev and Flight Engineer Alexander Lazutkin who are returning home after 185 days in space. The Soyuz vehicle carrying the Mir 23 crew home undocked from the station. Robinson again used the Southwest Ultraviolet Imaging System (SWUIS), a 7-inch imaging telescope that is pointed out of the orbiter's middeck hatch window, to observe the Hale-Bopp comet. Curbeam continued his work with the Bioreactor Demonstration System designed to perform cell biology experiments under controlled conditions. Tryggvason spent part of his time troubleshooting a computer hard drive system that supports the Microgravity Vibration Isolation Mount experiment.

Source record↗
NASA NTRS1997

STS-85 Day 09 Highlights

On this ninth day of the STS-85 mission, the flight crew, Cmdr. Curtis L. Brown, Jr., Pilot Kent V. Rominger, Payload Cmdr. N. Jan Davis (Ph.D.), Mission Specialists Robert L. Curbeam, Jr. and Stephen K. Robinson (Ph.D.), and Payload Specialist Bjarni V. Tryggvason watch over the Manipulator Flight Demonstration (MFD) experiment while Japanese investigators again maneuvere the Small Fine Arm remotely from a control room near Mission Control. It is the final planned work with the arm during this mission. While MFD operations are ongoing, Robinson again uses the Southwest Ultraviolet Imaging System's ultraviolet imaging telescope to observe Comet Hale-Bopp and Curbeam continue his work with the Bioreactor Demonstration System designed to perform cell biology experiments under controlled conditions. Tryggvason spends his day supporting data gathering with the Microgravity Vibration Isolation Mount experiment. Before the crew's workday began, they discussed the mission's progress with reporters in the U.S. and Canada as part of the traditional crew news conference. Questions ranged from life in space for the first time space travelers to providing a report card on the more than 24 experiments being conducted throughout the mission.

Source record↗
NASA NTRS1997

Reconsidering the Theological and Ethical Implications of Extraterrestrial Life

As we stand on the threshold of a new millennium, we also find ourselves at the brink of a new and exciting era in space exploration. In fact, this new era has already begun, with the successful landing and exploration of Mars by the Pathfinder mission in July 1997. Pathfinder represents an important scientific accomplishment for NASA because it demonstrated the agency's ability to successfully explore space at a relatively modest price. At the same time, Pathfinder revealed once again the genuine interest and fascination that people all over planet Earth have for space exploration. The Pathfinder mission is just one of several recent events-both scientific and cultural-that reveal this deep and almost unquenchable curiosity about space-and the possibility that there is life "out there." In August 1996, the public was captivated with NASA's announcement that a meteorite from Mars may contain evidence of early microscopic life. Shortly after the NASA announcement, media coverage of the discovery-and public discourse concerning the discovery-turned to an examination of the theological implications of evidence for extraterrestrial, albeit unintelligent, life. To a lesser extent, public reaction to the Hale-Bopp comet in the Spring of 1996 is also suggestive of many persons' deep passion to know more about space.

Randolph, Richard O.↗