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asteroids
This document provides an overview of asteroids, including their sizes, where they are located, and where they come from. It discusses how asteroids are studied and examples of asteroid missions. The document addresses why asteroids are of interest and the different levels of impact threats they pose to Earth, from small localized impacts to large civilization-ending impacts. It provides statistics on impact frequencies and examples of impact effects. Finally, it discusses strategies that can be used to detect, deflect, or destroy asteroids to mitigate impact risks.
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asteroids
- 1. What is anAsteroid?
- 4.
- 5. Where are they? Wheredo they come from?
- 7.
- 10. How do westudy asteroid?
- 11. LINEAR NEO SearchSystems
- 12. Asteroids: Years ofDiscovery 1
- 13.
- 16.
- 19. Hayabusa Visiting AsteroidItokawa
- 20. Hayabusa Visiting AsteroidItokawa
- 21. Why are weinterested in Asteroids?
- 24. What happens ifan Asteroid hits the Earth?
- 30. Earth Sterilizing Impact MassExtinction Impact Civilization Threatening Impact
- 31. What Happens Whenan Impact Takes Place? Bolides (up to 5 MT) • Great fireworks display, no damage Tunguska-class (15 MT) impact • Damage similar to large nuclear bomb (city-killer) • Average interval for whole Earth: 100 yr. • Minor risk relative to other natural disasters (earthquakes, etc.) Larger local or regional catastrophes (e.g. 10,000 MT) • Destroys area equivalent to small country • Average interval for whole Earth: 100,000 yr. • Moderate risk relative to other natural disasters Global catastrophe (> 1 million MT) • Global environmental damage, threatening civilization • Average interval for whole Earth: 1 million years • Major risk relative to other natural disasters
- 32.
- 35. Terrestrial Impact Frequency year century million yr. billionyr. ten thousand yr. 100 millionmillion10,00010010.01 Hiroshima Tunguska K/T TNT equivalent yield (MT) Global catastrophe Tsunami danger
- 36. What Can WeDo?
- 37. Strategies • Detect Project NEO(Near Earth Objects) http://neo.jpl.nasa.gov/ • Deflect Gravitational Tractor Impactor • Destroy
- 38. LINEAR NEO SearchSystems
- 41.
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- 43.
- 44.
- 45. Known Kilometer-Size NearEarth Asteroids 1000 500 1990 1995 2000 estimated total NEAs > 1 km Spaceguard official start
- 51. Looks like apotato?
Editor's Notes
- #4 http://neo.jpl.nasa.gov/images/composite.jpg http://neo.jpl.nasa.gov/images/gaspra.html These are views of the three asteroids that have been imaged at close range by spacecraft. The image of Mathilde (left) was taken by the NEAR spacecraft on June 27, 1997. Images of the asteroids Gaspra (middle) and Ida (right) were taken by the Galileo spacecraft in 1991 and 1993, respectively. All three objects are presented at the same scale. The visible part of Mathilde is 59 km wide x 47 km high (37 x 29 miles). Mathilde has more large craters than the other two asteroids. The relative brightness has been made similar for easy viewing; Mathilde is actually much darker than either Ida or Gaspra.
- #5 Ceres = 487 Vesta = 343 Eros – 14 Gaspara = 10 x 6 Exploring Meteorite mysteries.pdf http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Meteoroids.to.Meteorites/Exploring.Meteorite.Mysteries/.index.html http://www.jpl.nasa.gov/releases/2000/kleopatra.html http://neo.jpl.nasa.gov/images/ida.html http://neo.jpl.nasa.gov/images/gaspra.html
- #7 Exploring Meteorite mysteries.pdf http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Meteoroids.to.Meteorites/Exploring.Meteorite.Mysteries/.index.html
- #10 Exploring Meteorite mysteries.pdf http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Meteoroids.to.Meteorites/Exploring.Meteorite.Mysteries/.index.html
- #12 http://impact.arc.nasa.gov/
- #13 CERES -= 587 miles across Vesta = 343 miles Eros = 15 miles
- #14 http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001066.html GRIN NASA Center: Johnson Space Center Image # : STS082-709-097 Date : 02/19/1997 Hubble Redeployment Full Description Attached to the "robot arm" the Hubble Space Telescope is unberthed and lifted up into the sunlight during this the second servicing mission designated HST SM-02. Keywords STS-82 Discovery Payload Bay Hubble Space Telescope HST Remote Manipulator System RMS Canada Arm Subject Category Space Shuttle, Hubble, Reference Numbers Center: JSC Center Number: STS082-709-097 GRIN DataBase Number: GPN-2000-001066
- #15 http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000672.jpg GRIN NASA Center: Kennedy Space Center Image # : 89PC-0732 Date : 8/3/1989 Galileo Preparations Full Description In the Vertical Processing Facility (VPF), the spacecraft Galileo is prepared for mating with the Inertial Upper Stage booster. Galileo will be launched aboard the Orbiter Atlantis on Space Shuttle mission STS-34, October 12, 1989 and sent to the planet Jupiter, a journey which will take more than six years to complete. Keywords Galileo STS-34 Atlantis Vertical Processing Facility VPF Subject Category Planet-Jupiter, Voyager-Galileo, Reference Numbers Center: KSC Center Number: 89PC-0732 GRIN DataBase Number: GPN-2000-000672 Source Information Creator/Photographer: NASA Original Source: DIGITAL
- #16 http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1996-008A NEAR Shoemaker NSSDC ID:1996-008A Other Name(s) Near Earth Asteroid Rendezvous NEAR 23784 -------------------------------------------------------------------------------- Launch Date/Time: 1996-02-17 at 20:43:27 UTC On-orbit dry mass: 487 kg Nominal Power Output: 1800 W -------------------------------------------------------------------------------- Description The Near Earth Asteroid Rendezvous - Shoemaker (NEAR Shoemaker), recently renamed in honor of Gene Shoemaker, is designed to study the near Earth asteroid Eros from close orbit over a period of a year. The primary scientific objectives of NEAR are to return data on the bulk properties, composition, mineralogy, morphology, internal mass distribution and magnetic field of Eros. Secondary objectives include studies of regolith properties, interactions with the solar wind, possible current activity as indicated by dust or gas, and the asteroid spin state. This data will be used to help understand the characteristics of asteroids in general, their relationship to meteorites and comets, and the conditions in the early solar system. To accomplish these goals, the spacecraft is equipped with an X-ray/gamma ray spectrometer, a near infrared imaging spectrograph, a multi-spectral camera fitted with a CCD imaging detector, a laser rangefinder, and a magnetometer. A radio science experiment will also be performed using the NEAR tracking system to estimate the gravity field of the asteroid. The total mass of the instruments is 56 kg, and they require 81 W power. Mission Profile The ultimate goal of the mission is to study the near Earth asteroid 433 Eros from orbit for approximately one year. Eros is an S-class asteroid approximately 13 x 13 x 33 km in size, the second largest near-Earth asteroid. Initially the orbit will was circular with a radius of 200 km. The radius of the orbit was brought down in stages to a 50 x 50 km orbit on 30 April 2000 and decreased to 35 x 35 km on 14 July 2000. The orbit was raised over succeeding months to a 200 x 200 km orbit and then slowly decreased and altered to a 35 x 35 km retrograde orbit on 13 December 2000. The mission will end with a touchdown in the "saddle" region of Eros on 12 February 2001. After launch on a Delta 7925-8 (a Delta II Lite launch vehicle with nine strap-on solid-rocket boosters and a Star 48 (PAM-D) third stage) and exit from Earth orbit, NEAR entered the first part of its cruise phase. It spent most of this phase in a minimal activity "hibernation" state, which ended a few days before the flyby of the 61 km diameter asteroid 253 Mathilde on June 27, 1997. The spacecraft flew within 1200 km of Mathilde at 12:56 UT at 9.93 km/sec, returning imaging and other instrument data. On July 3, 1997 NEAR executed the first major deep space maneuver, a two-part burn of the main 450 Newton thruster. This decreased the velocity by 279 m/sec and lowered perihelion from 0.99 AU to 0.95 AU. The Earth gravity assist swingby occurred on January 23, 1998 at 7:23 UT. The closest approach was 540 km, altering the orbital inclination from 0.5 to 10.2 degrees, and the aphelion distance from 2.17 to 1.77 AU, nearly matching those of Eros. Instrumentation was active at this time.
- #17 http://impact.arc.nasa.gov/
- #18 http://near.jhuapl.edu/iod/20010208/index.html NEAR Shoemaker's Path This plot shows NEAR Shoemaker's projected path from orbit to the surface of Eros on Feb. 12. Viewed from the sun, Eros is moving in a clockwise direction as it spins on its axis, while the spacecraft moves counterclockwise in a circular orbit 35 kilometers (22 miles) from the asteroid's center. The pair will be about 316 million kilometers (196 million miles) from Earth. NEAR Shoemaker will de-orbit with a short engine burn at 10:31 a.m. EST, about 4 ½ hours before it's scheduled to reach the surface. The final leg of the controlled descent begins with the spacecraft about 5 kilometers (3 miles) above Eros; it will then execute an unprecedented series of four engine burns designed to slow its descent from about 20 mph to about 5 mph. NEAR Shoemaker is expected to touch down in an area bordering Himeros, the asteroid's distinctive saddle-shaped depression, after providing the highest-resolution images ever taken of Eros' boulder-strewn, cratered terrain.
- #19 http://near.jhuapl.edu/iod/20010131/index.html Closing in on Eros These four images are among thousands NEAR Shoemaker acquired during several low-altitude passes over Eros from January 25-28, 2001. From upper left to lower right, the images show Eros' bouldery surface at increasing resolution. The image at upper left was taken January 27 of a point 13.5 kilometers (8.4 miles) away; the one at the upper right was taken January 26 from 11.1 kilometers (6.9 miles) away. Each top scene is about 550 meters (1,815 feet) across. The image at bottom left was taken January 26 from 4.9 kilometers (3 miles) away, and the bottom right image was taken January 28 from a similar distance. Each lower scene is about 230 meters (760 feet) across. (Images 0155981852, 0155883236, 0155888661, 0156087736)
- #20 http://www.hayabusa.isas.jaxa.jp/e/index.htmlHayabusa
- #21 http://www.isas.ac.jp/e/snews/2005/1124_hayabusa.shtml Hayabusa Landed on and Took Off from Itokawa successfully Detailed Analysis Revealed Hayabusa attempted its first soft-landing on Itokawa for the purpose of touch down and sample collection on November 20-21, 2005. Below is the data information with the related advance report on its status.Hayabusa started descending at 9:00pm on Nov. 19th, 2005 (JST) from 1km in altitude. The guidance and navigation during the process of approach was operated normally, and at 4:33am on Nov. 20th, the last approach of vertical descent was commanded from ground, of which soft-landing was successfully achieved almost on the designated landing site of the surface. Deviation from the target point is now under investigation but presumed within a margin of 30m. The approaching trajectories in the quasi-inertial coordinate system and Itokawa-fixed coordinate system are shown in Data-1. Information on the altitude and its rate during the descent as measured by Doppler data is shown in Data-2. The velocity at the time of starting descent was 12cm/sec. At the altitude 54m at 5:28am, wire-cutting of target marker was commanded, after which, at 5:30am at altitude 40m, the spacecraft autonomously reduced its own speed by 9cm/sec to have substantially separated the target marker. It means that Hayabusa's speed became 3 cm/sec. Separation and freefall of the marker was confirmed from the image (Data-3) as well as from descending velocity of the spacecraft at the time of reducing the speed. The marker is presumed to have landed on southwest (upper right on the image) of MUSES Sea. Hayabusa then switched its range measurement from Laser Altimeter (LIDAR) to Laser Range Finder (LRF) at the altitude 35m and moved to hovering by reducing descending speed to zero at 25m above the surface, below where Hayabusa, at 5:40am at altitude 17m, let itself to freefall, functioning itself to the attitude control mode adjustable to the shapes of the asteroid surface. At this point, the spacecraft autonomously stopped telemetry transmission to the earth (as scheduled) to have changed to transmission with beacon mode more efficient for Doppler measurement by switching to low gain antenna (LGA) coverable larger area. Since then, checking of the onboard instruments was not possible on a real time basis (as scheduled), but as a result of analyzing the data recorded onboard and sent back to the earth in the past two days, Hayabusa seemed to have autonomously judged to abort descending and attempted emergency ascent because its Fan Beam sensors for obstacle checking detected some kind of catch-light. Allowable margin is set for Hayabusa for its attitude control, in the case the spacecraft takes off the ground by accelerating the velocity on its own. Under such circumstances, the then spacecraft's attitude was out of the margin, because of which continuing of safe descent was consequently chosen. As a result, Hayabusa did not activate its Touch Down Sensor function. At the timepoint of Nov. 21, Hayabusa was judged not to have landed on the surface. According to the replayed data, however, it was confirmed that Hayabusa stayed on Itokawa by keeping contact with the surface for about 30 minutes after having softly bounced twice before settling. This can be verified by the data history of LRF and also by attitude control record (Data-4).This phenomenon took place during switching interval from Deep Space Network (DSN) of NASA to Usuda Deep Space Center, because of which the incident was not detected by ground Doppler measurement. The descending speed at the time of bouncing twice was 10cm/sec. respectively. Serious damage to the spacecraft has not been found yet except heating sensor that may need checking in some part of its instrument.Hayabusa kept steady contacting with the surface until signaled from ground to make emergency takeoff at 6:58am (JST). The Touch Down Sensor supposed to function for sampling did not work because of the reason above stated, for which reason firing of projector was not implemented in spite of the fact that the spacecraft actually made landing. The attitude at landing is so presumed that the both bottom ends of +X axis of sampler horn and either the spacecraft or tip end of the solar panels was in contact with the surface. Hayabusa became the world-first spacecraft that took off from the asteroid. Really speaking, it is the world-first departure from an celestial body except the moon. After departure from the asteroid by ground command, Hayabusa moved into safe mode due to the unsteady communication line and the conflict with onboard controlling and computing priority. The comeback from safety mode to normal 3-axis control mode needed full two days of Nov. 21 and 22. Owing to this reason, replaying of the data recorded on 20th is still midway, which means the possibility to reveal much more new information through further analysis of the data. As of now, the detailed image of the landing site to know its exact location has not been processed yet. Hayabusa is now on the way to fly over to the position to enable landing and sampling sequence again. It's not certain yet if or not descent operation will be able to carry out from the night of Nov. 25 (JST). We will announce our schedule in the evening of Nov. 24. Descending and landing operation will all depend upon availability of DSN of NASA. We would like to express our sincere gratitude for cooperation of NASA for tracking networks including backup stations. (Data-1) Approach to Itokawa and descending trajectory Figures below indicate approaching trajectory of Hayabusa at descending and landing on Nov. 20th. Fig. 1a describes the trajectory in quasi-inertial coordinate system with z-axis (bottom of fig.) directed toward the earth. Fig. 1b describes the trajectory as against the Itokawa-fixed coordinate system. The trajectory plan was altered according to the occasion during its operation but it is clear from the figure that actual flight route was very close to the one planned in advance. Fig. 1a: Actual descending trajectory as compared to the scheduled plan.(Quasi-inertial coordinate system) Fig. 1b: Actual descending trajectory as compared to the scheduled plan.(Itokawa-fixed coordinate system) Fig. 1c is to comply with fig. 1a to show actual trajectory overlapped on alternated trajectory plan subject to changes from time to time according to the occasional situation. Each dot indicates the location of the spacecraft presumed on ground from the surface shapes by processing the compressed image data occasionally. Figures show that guidance was carried out almost according to the scheduled trajectory. Fig. 1c: Navigation and guidance (Quasi-inertial system) From further up in altitude, the dotted locations presumed from the surface shapes vary with discrepancy but from below 1km sufficiently reliable information is obtained. The figure shows that the spacecraft was precisely guided according to re-scheduled trajectory plan. (Data 2): Data history of descending altitudes to Itokawa and its descending rate. Fig. 2a is the Doppler velocity history measured at Usuda and DSN stations, which roughly indicates the descending velocity of Hayabusa to Itokawa. The figure shows that the velocity of Hayabusa at the start of vertical descent was about 12cm/sec. and that the spacecraft reduced its speed autonomously controlling the velocity accelerated by the gravity of the asteroid.Fig. 2b shows the updated altitude information at the right timing that was presumed from the surface conditions by integrating Doppler velocity information. The figure indicates the approximate altitude from the center of the asteroid mass. The dotted green line in the figure indicates the altitudes from the surface of ITOKAWA measured by laser altimeter. We can roughly understand the situation of each event at the time of happening by referring to both data of laser altimeter and Doppler velocity information. Fig. 2a: Doppler measurement during descent of Hayabusa Fig. 2b: Altitude history of Hayabusa during descent(or distance history from the center of the asteroid mass). The increase in Doppler velocity at 5:40am (JST) (21:40 world time) is because of landing on the surface of Itokawa as further explained below. From then on, tracking was switched to Usuda station, because of which we could not obtain Doppler velocity information for a while but the movement of the spacecraft was partly known from LRF, of which data has been partly analyzed as to the later movement of the spacecraft. (Data 3) Target marker with 880,000 names separated from Hayabusa and tracking from aboard. The target marker was released from the spacecraft at the relative velocity of 9cm/sec. The delivery location is southwest of (right under in fig. 3) MUSES Sea. The target marker was designed to reduce bouncing rate by appropriately filling up the inside of aluminum sphere with fine pellets made of high-polymer materials to induce multiple collisions inside to increase consumption of energy. The marker was developed through repeated tests conducted on ground as well as in a non-gravity vacuum tube to prove its low repulsion.
- #23 http://spaceflight.nasa.gov/gallery/images/mars/asteroids/html/s78_27139.html S78-27139 (June 1977)--- This painting shows an asteroid mining mission to an Earth-approaching asteroid. Asteroids contain many of the major elements which provide the basis for industry and life on Earth. A NASA-sponsored study on space manufacturing held at Ames Research Center (ARC) in summer of 1977 provided much of the technical basis for the painting. "Asteroid-1" is the central long structure and the propulsion unit is the long tubular structure enveloped by stiffening yard arms and guy wires. Solar cells running the length of the propulsion system convert the sunlight into electricity which is used to power the propulsion system. During the mission these solar arrays would be oriented toward the Sun to gather maximum power. In the left foreground is an asteroid mining unit, doing actual mining work. An orbital construction platform in permanent orbit provides power, supplies depot and work volume within which work proceeds. Artist concept by Denise Watt. Note: NASA currently has no formal plans for a human expedition to Mars or the Moon. This image and others displayed may not reflect the hardware and overall concept of possible visits to either of those celestial bodies. However, the art work represented here serves as a comprehensive study of various concepts and ideas developed as possibilities over a period of years. The renderings were accomplished by NASA and/or NASA-commissioned artists.
- #27 http://www.angelfire.com/ut/aylett/images/Moon.jpg
- #28 http://antwrp.gsfc.nasa.gov/apod/ap981008.html Far Side of the Moon Credit: Apollo 16, NASA Explanation: Locked in synchronous rotation, the Moon always presents its well-known near side to Earth. But from lunar orbit, Apollo astronauts also grew to know the Moon's far side. This sharp picture from Apollo 16's mapping camera shows the eastern edge of the familiar near side (left) and the strange and heavily cratered far side of the Moon. Surprisingly, the rough and battered surface of the far side looks very different from the near side which is covered with smooth dark lunar maria. The likely explanation is that the far side crust is thicker, making it harder for molten material from the interior to flow to the surface and form the smooth maria.
- #29 http://www.lpi.usra.edu/research/lunar_orbiter/img/4-124H2.jpg http://www.lpi.usra.edu/htbin/lunar_orbiter/lo.pl?info1257 Photo Number IV-124-H2 Feature Name: Tycho Feature Latitude: 43.4°S Feature Longitude: 11.1°W Size: 102 km Sun Angle: 70.1° Spacecraft Altitude: 2994.47 km Medium Photo Center Latitude: 43°S Medium Photo Center Longitude: 14.08°W Add crater close up chart
- #30 Add crater forming chart http://cass.jsc.nasa.gov/education/EPO/explore/craters.pdf http://cass.jsc.nasa.gov/expmoon/science/craterstructure.html Barringer Meteor Crater, Arizona Meteor Crater is one of the youngest and best-preserved impact craters on Earth. The crater formed roughly 50,000 years ago when a 50-meter-wide iron-rich meteor weighing 100,000 tons struck the Arizona desert at an estimated 20 kilometers per second. The resulting explosion exceeded the combined force of today's nuclear arsenals and created a 1.1-kilometer-wide, 200-meter-deep crater. Meteor Crater is a simple crater since it has no central peak or rim terraces. The crater formed in layered sedimentary rocks, some of which are exposed in the nearby Grand Canyon. These rocks have been uplifted and in some cases overturned at the crater's raised rim. Debris sliding and subsequent erosion have partially filled the bottom of the crater with minor amounts of rim material and sediment. The heavily cratered history of the Moon indicates that Earth also experienced many impact events early in its history. The processes of erosion and plate tectonics have combined to erase nearly all Earth's craters. To date, only about 150 impact craters have been identified on Earth, and most of those are severely eroded or buried by later rock units. This aerial view shows the dramatic expression of the crater in the arid landscape. — Credit: D. Roddy, U.S. Geological Survey
- #32 http://impact.arc.nasa.gov/
- #34 http://nssdc.gsfc.nasa.gov/planetary/sl9/image/sl9may_hst.gif http://nssdc.gsfc.nasa.gov/planetary/sl9/html/preimpact_images.html HOTO RELEASE NO.: STScI-PR94-26cFOR RELEASE: Thursday, July 7, 1994 HUBBLE'S PANORAMIC PICTURE OF COMET SHOEMAKER-LEVY 9 A NASA Hubble Space Telescope (HST) image of comet P/Shoemaker-Levy 9, taken on May 17, 1994, with the Wide Field Planetary Camera-2 (WFPC-2) in wide field mode. When the comet was observed, its train of 21 icy fragments stretched across 710 thousand miles (1.1 million km) of space, or 3 times the distance between Earth and the Moon. This required 6 WFPC exposures spaced along the comet train to include all the nuclei. The image was taken in red light. The comet was approximately 410 million miles (660 million km) from Earth when the picture was taken, on a mid-July collision course with the gas giant planet Jupiter. Credit: H.A. Weaver, T. E. Smith (Space Telescope Science Institute), and NASA
- #35 http://nssdc.gsfc.nasa.gov/planetary/sl9/image/sl9juppre_hst.gif http://nssdc.gsfc.nasa.gov/planetary/sl9/html/preimpact_images.html PHOTO RELEASE NO.: STScI-PR94-26a FOR RELEASE: July 7, 1994 PHOTO ILLUSTRATION OF COMET P/SHOEMAKER-LEVY 9 & PLANET JUPITER This is a composite photo, assembled from separate images of Jupiter and comet P/Shoemaker-Levy 9, as imaged by the Wide Field & Planetary Camera-2 (WFPC-2), aboard NASA's Hubble Space Telescope (HST). Jupiter was imaged on May 18, 1994, when the giant planet was at a distance of 420 million miles (670 million km) from Earth. This "true-color" picture was assembled from separate HST exposures in red, blue, and green light. Jupiter's rotation between exposures creates the blue and red fringe on either side of the disk. HST can resolve details in Jupiter's magnificent cloud belts and zones as small as 200 miles (320 km) across (wide field mode). This detailed view is only surpassed by images from spacecraft that have traveled to Jupiter. The dark spot on the disk of Jupiter is the shadow of the inner moon Io. This volcanic moon appears as an orange and yellow disk just to the upper right of the shadow. Though Io is approximately the size of Earth's Moon (but 2,000 times farther away), HST can resolve surface details. When the comet was observed on May 17, its train of 21 icy fragments stretched across 710 thousand miles (1.1 million km) of space, or 3 times the distance between Earth and the Moon. This required six WFPC exposures along the comet train to include all the nuclei. The image was taken in red light. The apparent angular size of Jupiter relative to the comet, and its angular separation from the comet when the images were taken, have been modified for illustration purposes. Credit: H.A. Weaver, T.E. Smith (Space Telescope Science Institute) and J.T. Trauger, R.W. Evans (Jet Propulsion Laboratory), and NASA
- #36 http://impact.arc.nasa.gov/
- #39 http://impact.arc.nasa.gov/
- #43 http://impact.arc.nasa.gov/
- #44 http://impact.arc.nasa.gov/
- #45 http://impact.arc.nasa.gov/
- #46 NASA ARC http://impact.arc.nasa.gov/
- #47 http://neo.jpl.nasa.gov/images/ida.html This color picture is made from images taken by the imaging system on the Galileo spacecraft about 14 minutes before its closest approach to asteroid 243 Ida on August 28, 1993. Asteroid 243 Ida & Dactyl August 28, 1993 The range from the spacecraft was about 10,500 kilometers (6,500 miles). The images used are from the sequence in which Ida's moon was originally discovered; the moon is visible to the right of the asteroid. This picture is made from images through the 4100-angstrom (violet), 7560 A (infrared) and 9680 A (infrared) filters. The color is 'enhanced' in the sense that the CCD camera is sensitive to near infrared wavelengths of light beyond human vision; a 'natural' color picture of this asteroid would appear mostly gray. Shadings in the image indicate changes in illumination angle on the many steep slopes of this irregular body as well as subtle color variations due to differences in the physical state and composition of the soil (regolith). There are brighter areas, appearing bluish in the picture, around craters on the upper left end of Ida, around the small bright crater near the center of the asteroid, and near the upper right- hand edge (the limb). This is a combination of more reflected blue light and greater absorption of near infrared light, suggesting a difference in the abundance or composition of iron- bearing minerals in these areas. Ida's moon also has a deeper near-infrared absorption and a different color in the violet than any area on this side of Ida. The moon is not identical in spectral properties to any area of Ida in view here, though its overall similarity in reflectance and general spectral type suggests that it is made of the same rock types basically. These data, combined with study of further imaging data and more detailed spectra from the Near Infrared Mapping Spectrometer, may allow scientists to determine whether the larger parent body of which Ida, its moon, and some other asteroids are fragments was a heated, differentiated object or made of relatively unaltered primitive chondritic material. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory.
- #48 http://near.jhuapl.edu/iod/20000214f/index.html NEAR image of the day for 2000 Feb 14 (F) NEAR's last image returned before orbit insertion On February 12, two days before NEAR's insertion into orbit around Eros, the spacecraft's camera took this image of Eros from a range of 970 miles (1570 kilometers). This was the last image returned to Earth prior to NEAR's insertion into Eros orbit. Features as small as a 520 feet (160 meters) across can be seen. This face of Eros is dominated by a huge, hollowed-out gouge which may also have been caused by an impact. The feature which from a greater distance appears heart-shaped (at lower left) is resolved in this view as three impact craters which rims shallow depression. (Image 0125766481)
- #49 http://near.jhuapl.edu/NEAR/iod/20000214b/20000214b.jpg http://near.jhuapl.edu/NEAR/iod/20000214b/index.html NEAR's road to Eros This montage shows a selection of images of the asteroid 433 Eros that were acquired from the NEAR spacecraft over three weeks from January 22 through February 12, 2000, as the spacecraft's distance from its target shrank from 18,000 to 1260 miles (29,000 to 2025 km). As the spacecraft closed in on its target, the resolution of the images increased from 1.7 to 0.12 miles (2.8 to 0.19 km) per pixel. At 20x8x8 miles in size (33x13x13 kilometers), Eros is the second largest near-Earth asteroid and spins on its axis once every 5 hours, 16 minutes. During the early stages of NEAR's approach, Eros appeared as a small blob only a few pixels across. The apparent size of Eros and the resolution of the pictures increased continuously, at first only slowly and later dramatically day by day until, on February 9, the level of detail visible exceeded that during NEAR's first flyby of Eros on December 23, 1998. In the last images shown here, details of Eros's surface have become visible. Heavy cratering has pockmarked the irregular asteroid's surface. One side is dominated by a scallop-rimmed gouge, and the opposite side by a conspicuous, raised-rimmed crater. (Images 0124182130, 0124185068, 0124188103, 0124191138, 0124194173, 0124197034, 0124200069, 0124203051, 0124206021, 0124206397, 0124209013, 0124212066, 0124215044, 0124263133, 0124266253, 0124269373, 0124272493, 0124275613, 0124278733, 0124281853, 0124543933, 0124547053, 0124550173, 0124553293, 0124556413, 0124561093, 0124562653, 0124772331, 0125039735, 0125056325, 0125059465, 0125062605, 0125065745, 0125068885, 0125075950, 0125104854, 0125123255, 0125137235, 0125209535, 0125218007, 0125221023, 0125224039, 0125227003, 0125230019, 0125236153, 0125239046, 0125242991, 0125245884, 0125248245, 0125252196, 0125255087, 0125270154, 0125312200, 0125324200, 0125342200, 0125389000, 0125460640, 0125494933, 0125501173, 0125507413, 0125513653, 0125640955, 0125647625, 0125650641, 0125653631, 0125656621, 0125659611, 0125662627, 0125665617, 0125693155, 0125720155) http://antwrp.gsfc.nasa.gov/apod/ap000216.html Credit: NEAR Project, JHU APL, NASA Explanation: On February 14th, the NEAR spacecraft became the first artificial moon of an asteroid. Captured by the gentle gravity of a 20 mile long slipper-shaped mountain of rock, NEAR recorded this premier image while orbiting asteroid 433 Eros at a distance of about 200 miles. The image shows features as small as 100 feet across in a view dominated by a 3 mile wide crater near Eros' narrow waist. Enticing layers and grooves are visible within the crater rim along with an enormous 170 foot boulder lying on the crater floor (near picture center). Although Eros is a large S-type near-earth asteroid, it is still not massive enough for its own gravity to have shaped it into a planet-like spherical form. By comparison, Eros has less than a thousandth Earth's gravity, so a 100 pound object on Earth would weigh about 1 ounce on Eros. A baseball thrown at 22 miles per hour would completely escape into space. The weak gravity and irregular shape make orbiting Eros a delicate challenge for NEAR's controllers who plan a year long exploration program with possible close approaches to the asteroid's surface.
- #50 http://www.sciencemag.org/cgi/content/full/292/5516/484#F1 Fig. 1. Typical segment of LAF coverage (right) centered at (24.1°S, 19.2°W). The region (left) is located in the vicinity of crater Selene (which is about 3 km in diameter) and is representative of the cratered terrains on Eros. The closeup view at right is a mosaic of four frames at mission elapsed time (MET) 147953203 to 147953253 s and has a scale of about 1.2 m per pixel. The context view at left is a mosaic of frames at MET 145906548 to 145906743 s. [View Larger Version of this Image (58K GIF file)] Imaging of Small-Scale Features on 433 Eros from NEAR: Evidence for a Complex Regolith J. Veverka,1 P. C. Thomas,1 M. Robinson,2 S. Murchie,3 C. Chapman,4 M. Bell,1 A. Harch,1 W. J. Merline,4 J. F. Bell III,1 B. Bussey,2 B. Carcich,1 A. Cheng,3 B. Clark,1 D. Domingue,3 D. Dunham,3 R. Farquhar,3 M. J. Gaffey,5 E. Hawkins,3 N. Izenberg,3 J. Joseph,1 R. Kirk,6 H. Li,2 P. Lucey,7 M. Malin,8 L. McFadden,9 J. K. Miller,10 W. M. Owen Jr.,10 C. Peterson,1 L. Prockter,3 J. Warren,3 D. Wellnitz,9 B. G. Williams,10 D. K. Yeomans10 On 25 October 2000, the Near Earth Asteroid Rendevous (NEAR)-Shoemaker spacecraft executed a low-altitude flyover of asteroid 433 Eros, making it possible to image the surface at a resolution of about 1 meter per pixel. The images reveal an evolved surface distinguished by an abundance of ejecta blocks, a dearth of small craters, and smooth material infilling some topographic lows. The subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter-sized blocks. 1 Space Sciences Building, Cornell University, Ithaca, NY 14853, USA. 2 Department of Geological Sciences, Northwestern University, 309 Locy Hall, Evanston, IL 60208, USA. 3 Applied Physics Laboratory, Johns Hopkins University, 1110 Johns Hopkins Road, Laurel, MD 20723, USA. 4 Southwest Research Institute, 1050 Walnut Street, Suite 426, Boulder, CO 80302, USA. 5 Department of Earth and Environmental Sciences, Science Center, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180-3590, USA. 6 U.S. Geological Survey, 2255 North Gemini Drive, Flagstaff, AZ 86001, USA. 7 Hawaii Institute of Geophysics and Planetology, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822, USA. 8 Malin Space Science Systems, Post Office Box 910148, San Diego, CA 92191, USA. 9 Department of Astronomy, University of Maryland, College Park, MD 20742, USA. 10 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA. Volume 292, Number 5516, Issue of 20 Apr 2001, pp. 484-488. Copyright © 2001 by The American Association for the Advancement of Science. All rights reserved.
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- #52 http://www.ndsu.nodak.edu/instruct/gudmesta/lateblight/image3_3.html SILVER SCURF OF POTATO Gary A. Secor Department of Plant Pathology North Dakota State University Silver scurf disease of potato is caused by the fungus Helminthosporium solani. The disease has gone from obscurity to serious the past few years due to a number of factors including resistance to thiabendazole fungicides, improved storages with higher humidities, lowered defect tolerances, and increased awareness. It is a blemish disease of tubers, causing a metallic discoloration of the periderm in irregular patterns. It does not cause yield losses at harvest, but does cause weight loss of stored potatoes due to increased water loss, resulting in excess shrink and flabbiness. It affects quality of all market classes of potatoes. It is a cosmetic disease of red-skinned and russet fresh potatoes, resulting in reduced consumer acceptance and rejection, and after prolonged storage turns round reds into brown rounds. http://www.marthas-hosiery.com/DFW3-22001.html SB transport foam DF224-22001 crop poster 3 neg blue http://near.jhuapl.edu/media/image_sheets/heart.pdf http://near.jhuapl.edu/iod/20000929/index.html The Ups and Downs of Eros While NEAR Shoemaker does not directly measure gravity on Eros' surface, the spacecraft gathers other data that allow scientists to infer this measurement. Radio tracking has been analyzed to determine the asteroid's gravitational "pull" on the orbiting spacecraft. The many images of the asteroid, plus range measurements from the laser altimeter, measure the body's shape. Comparisons of the shape with the gravitational pull felt by the spacecraft from different parts of its orbit show that the density of the interior must be nearly uniform. The asteroid's shape, density and spin combine to create a bizarre pattern of what is "uphill" and "downhill." In this view, a map of "gravitational topography" has been painted onto a shape model. Red areas are "uphill" and blue areas are "downhill." A ball dropped onto one of the red spots would try to roll across the nearest green area to the nearest blue area. (Image copyright 2000 Science Magazine)
- #53 http://antwrp.gsfc.nasa.gov/apod/image/0111/leonid3_lodriguss.jpg http://antwrp.gsfc.nasa.gov/apod/ap011122.html 2001 November 22 Fireball, Smoke Trail, Meteor Storm Credit & Copyright: Jerry Lodriguss Explanation: Returning from orbit, space shuttles enter the atmosphere at about 8 kilometers per second as friction heats their protective ceramic tiles to over 1,400 degrees Celsius. By contrast, the bits of comet dust which became the Leonid meteors seen on November 18, were moving at 70 kilometers per second, completely vaporizing at altitudes of around 100 kilometers. In this single 5 minute time exposure, three Leonid meteors are shooting through skies above Spruce Knob, West Virginia, USA. Background stars are near the constellation Orion. The brightest meteor, a fireball, dramatically changes colors along its path and leaves a smokey persistant trail drifting in high-altitude winds. From that extremely dark site, at an elevation of 1,200 meters, astrophotographer Jerry Lodriguss reports, "We observed a [zenithal hourly rate] of about 3,600 at 10:30 UT and very high rates from 9:30 UT until well into the start of astronomical twilight at 10:50 UT. It was quite a spectacular storm, with bolides going off like flashbulbs, green and red fireballs and other fainter Leonids in all parts of the sky."
- #54 http://www.aero.org/leonid/leonid1.gif http://www.aero.org/leonid/test-leonids.html The Leonids--A Regular November Event Summary || Definitions || Meteor Shower Basics || The Leonids The Dangers || What Can be Done? || Plan for the Future The Leonids are the result of the passage of the Earth through the path of the debris cloud of the comet Tempel-Tuttle. The meteor activity associated with comet Tempel-Tuttle is called a "Leonid" event because the meteors appear to be coming from the direction of the constellation Leo. There is evidence that this comet has created meteor showers and meteor storms for more than 1,000 years. Tempel-Tuttle, named after Ernst Tempel and Horace Tuttle who first discovered the comet in 1865 and 1866, is about 4 km in diameter and orbits the Sun with a period of just over 33 years. As it makes its closest approach to the Sun, it passes close to the Earth's orbit (not the Earth, the Earth's orbit). The closest approach (called perihelion) occurred this year on February 28, 1998. The orbit of the comet crosses the orbit of Earth. Debris from the comet is spread along its orbit and causes annual Leonid meteor showers when the Earth passes through the area of space where the comet has been.
- #55 http://SpaceWeather.com/meteors/leonids/2001/zhr_imo_big.gif http://SpaceWeather.com/ http://science.nasa.gov/headlines/y2001/ast08nov_1.htm Table notes: (1) UT is Universal Time, also known as Greenwich Mean Time or GMT. UT values above refer to Nov. 18th. (2) Because of the international date line, observers in Australian and Asian countries will see their Leonids before dawn on Nov. 19th local time. (3) ZHR is the Zenithal Hourly Rate -- that is, the number of meteors a observer with ideally dark skies would see if the constellation Leo were directly overhead. The range in predicted ZHRs reflects differences among the models of various forecasters. [more information]
- #56 http://www.aero.org/leonid/leonid1.gif http://www.aero.org/leonid/test-leonids.html The Leonids--A Regular November Event Summary || Definitions || Meteor Shower Basics || The Leonids The Dangers || What Can be Done? || Plan for the Future The Leonids are the result of the passage of the Earth through the path of the debris cloud of the comet Tempel-Tuttle. The meteor activity associated with comet Tempel-Tuttle is called a "Leonid" event because the meteors appear to be coming from the direction of the constellation Leo. There is evidence that this comet has created meteor showers and meteor storms for more than 1,000 years. Tempel-Tuttle, named after Ernst Tempel and Horace Tuttle who first discovered the comet in 1865 and 1866, is about 4 km in diameter and orbits the Sun with a period of just over 33 years. As it makes its closest approach to the Sun, it passes close to the Earth's orbit (not the Earth, the Earth's orbit). The closest approach (called perihelion) occurred this year on February 28, 1998. The orbit of the comet crosses the orbit of Earth. Debris from the comet is spread along its orbit and causes annual Leonid meteor showers when the Earth passes through the area of space where the comet has been.