The Apollo asteroid Hermes approaches Earth's orbit twice every 777 days but often goes unnoticed. In 1980 this asteroid passed within 300,000 miles from Earth's orbit, only a little more than the distance from the Earth to the Moon. Despite this close encounter, its passage went unnoticed. It was rediscovered in 2003 and this time scientists used radar from the giant Arecibo antenna in Puerto Rico to take a closer look. They found that Hermes is in fact two asteroids linked together by their mutual gravitational attraction.
Source: Science at NASA, Image ID: echo_med.gif
A theory that suggests that the seeds of life on Earth came from space gained support recently, with the discovery of sugar and related organic compounds in meteorites. The meteorite shown here was found to contain molecules of organic compounds, indicating the possibility that some of the ingredients of the "primordial soup" were brought to our planet from beyond. For more details, try the reports from NASA Science News and CNN.
Source: Science at NASA, Image ID: CC3-72comp_sm.jpg
The NEAR mission to asteroid Eros was one of NASA's resounding successes, capturing the attention of the world for several months. The level of popular interest can easily be judged by the numerous entries in the Astronomy Picture of the Day. Highlights included landing on the asteroid's surface, a feat the spacecraft wasn't even designed to perform. After the successful touchdown, NEAR continued sending back data about the composition of the minor planet. The image linked at the top of this entry shows the last photo snapped while NEAR approached the surface; the bottom half is smeared because the camera was forced to quit working.
Source: Johns Hopkins University, NEAR Image of the Day, Image ID: 20010209.gif
On January 18, 2000, one of the most dramatic meteors in 10 years streaked across the skies of the Yukon Territory in Canada. Witnesses reported two sonic booms, a foul odor, and sizzling sounds heard all the way from Alaska through northwestern Canada. Based on readings from defense satellites and seismic monitoring stations, scientists estimated that the meteor exploded with the energy of two to three kilotons of TNT. Now, thanks to a resident of Canada who has requested anonymity, fragments of the meteorite have been recovered and turned over to scientists for analysis. The fragmentslumps of crumbly rock with scorched, pitted surfacesresemble partly used charcoal briquettes: black, porous, fairly light and still smelling of sulfur. Scientists say the meteorite was a carbonaceous chondrite, a rare type of space rock that contains many forms of carbon and organics, basic building blocks of life. Carbonaceous chondrites, which comprise only about 2 percent of meteorites known to have fallen to Earth, are typically difficult to recover because they easily break down during entry into Earth's atmosphere and during weathering on the ground. Zolensky says it's been 31 years since the last time a carbonaceous chondrite like this fell to Earth and was recovered.
Photo Credit: This sequence of pictures was captured by Ewald Lemke (Atlin Realty, Atlin, British Columbia) on January 18, 2000. It shows the expanding smoke train of the Yukon meteor over a 14-minute period. The first frame shows a smoky red vapor trail just 1 minute and 30 seconds after the initial flash.
Source: NASA Space Science News, Yukon Meteorite Recovered
This color picture was made from images taken by the Galileo spacecraft during its close approach to asteroid 243 Ida on August 28, 1993. The asteroid was discovered to have a small moon, visible on the right side of the picture. The tiny moon, dubbed Dactyl, is about 1.5 kilometers across, and is the first natural satellite of an asteroid ever to be discovered and photographed. The name is derived from the "Dactyli," a group of mythological beings who lived on Mount Ida. According to myths, the infant Zeus was hiddenand raised, in some accountsby the nymph Ida and protected by the Dactyli. Other mythological accounts say that the Dactyli were Ida's children by Zeus. In any case, the name seems appropriate.
Source: National Space Science Data Center, Photo Gallery: Asteroids, Image ID: idasmoon.jpg
This montage shows asteroid 951 Gaspra (top) compared with Deimos (lower left) and Phobos (lower right), the moons of Mars. Gaspra is about 17 kilometers long. The three bodies are shown at the same scale and nearly the same lighting conditions. All three bodies have irregular shapes due to past catastrophic conditions. Their surfaces appear remarkably different, however, possibly because of differences in composition, but most likely because of differences in their impact histories. Overall, the moons of Mars are more similar in composition to objects in the asteroid belt than to Mars itself.
Source: National Space Science Data Center, Photo Gallery: Asteroids, Image ID: NASA PR P-41382
This schematic image is from a series of drawings that illustrate the sequence of events that formed the Manicouagan crater. The meteorite or comet probably collided with the target region at a speed of about 60 kilometers per second, and exploded above, or near, the surface. A hemispherical transient crater was formed by the explosion. Part of the target rocks were melted and accumulated in a pool at the bottom of the crater. Concentric fault cracks formed, and huge blocks rotated towards the center, which lifted up to form the central peak. Slumping and erosion later lowered the level of the surrounding rocks and removed a substantial amount of material, perhaps as much as a kilometer in thickness, from the surface layers, leaving the outer annular ring lake and a central highland made of shocked rocks.
Source: Meteorite and Impacts Advisory Committee to the Canadian Space Agency, Crater Formation, Image ID: impact-5.jpg
The Manicouagan crater lies in northern Quebec, Canada (Lat 51° 23' N, Long 68° 42' W). It is one of the largest and oldest known, with a diameter of about 100 km. The crater is a multiple-ring structure, but the feature that shows up best in this NASA Landsat satellite photo is the inner ring, which is occupied by a lake (Manicouagan Reservoir) with an outer diameter of about 70 km. The impact occurred 214 million years ago. The asteroid probably had a diameter of about 5 km. It may have produced a mass extinction similar to that at the end of the Cretaceous period.
Source: Meteorite and Impacts Advisory Committee to the Canadian Space Agency, Impact Craters on Earth, Image ID: manic-l.jpg
On October 9, 1992, a meteor ended its flight over the eastern United States by crashing into a parked 1980 Chevy Malibu automobile. A portion of the resulting 12-kilogram chondritic meteorite is shown in this image. Part of the flight was recorded by spectators at a nearby football game near Peekskill, New York. Other pieces of this object are housed in the National Museum of Natural History of the Smithsonian Institution in Washington, D.C.
Source: Swiss Meteorite Laboratory, Gallery of Famous Meteorites, Image ID: peekskil.gif
The Martian meteorite EETA 79001, found in Antarctica. The cube beside the meteorite is 1 centimeter on a side. This meteorite is one of a class of objects known as the SNCs that contain traces of gas identical with the Martian atmosphere as analyzed by the Viking landers. Asteroid impacts ejected the meteorites off Mars into orbit around the Sun. Then, most likely after millions of years, some of these objects landed on Earth. Among other characteristics in common, these Martian meteorites are all volcanic rocks, mostly young (erupted only 180 million years ago), and almost all have reacted with Martian groundwater. These meteorites have helped to shape current theories about Mars's atmosphere, water, and geologic history.
Source: Lunar and Planetary Institute, Exploring Mars, Image ID: EETA 79001
Photographic data recorded at two or more locations allow the pre-collision orbits of meteoroids to be calculated, and the most likely area of fall for the final meteorite to be inferred. This schematic drawing shows the calculated orbits of several objects for which such photographic records are available. Note that the aphelia (farthest orbital points from the Sun) of many of these objects indicate that they may have originated in the asteroid belt between the orbits of Mars and Jupiter.
Source: Meteorite and Impacts Advisory Committee to the Canadian Space Agency, Meteorite Observation and Recording Program, Image ID: orbits.jpg
In 1950, Dutch astronomer Jan Oort hypothesized that comets came from a vast shell of icy bodies about 50,000 times farther from the Sun than is Earth. A year later astronomer Gerard Kuiper suggested that some comet-like debris from the formation of the solar system should also be found just beyond Neptune, and that a disk of such debris should naturally form around the edge of the solar system. As sensible as this suggestion may have been, the existence of the Kuiper belt remained a theory until the 1992 detection of a 150-mile-wide body called 1992QB1 at the distance of the suspected belt. Several similar objects were soon found in this Kuiper belt region. The planet Pluto, discovered by Clyde Tombaugh in 1930, is now considered the largest member of this region, and several smaller but similar "Plutoids" have been found that also orbit the Sun in 3:2 resonance orbits with respect to the orbit of the much larger planet Neptune. Neptune's satellites, Triton and Nereid, and Saturn's satellite, Phoebe, are also in unusual orbits and may in fact be captured Kuiper belt objects. This drawing shows the location of the Kuiper belt with respect to the solar system.
Source: NASA Space Telescope Science Institute, Hubble Space Telescope Public Pictures, Image ID: PR 95-26; (copyright notice)
Where do comets come from? In 1951, Gerard Kuiper proposed that a population of small bodies inhabits the furthest reaches of our solar system, and that some of these bodies occasionally stray closer to the Sun, thus becoming comets. An important confirmation of this conjecture was revealed when Dave Jewitt (University of Hawaii) and Jane Luu (University of California at Berkeley) discovered the small object in this photo -- its orbit is consistent with membership in the Kuiper Belt. If confirmed, this would be the first known member, and may help us to understand the source of comets, and the conditions in the early stages of our solar system.
Source: University of Hawaii, Institute for Astronomy, 1992 QB1. Image ID: qb1.gif
The Kuiper Belt Object "Quaoar," recently discovered by scientists using the Hubble Space Telescope, is about 800 miles (1300 kilometers) in diameter. That makes it the largest solar system object found since the discovery of Pluto 72 years ago. The image here, described more fully at Hubble's website, shows the path of Quaoar, and a zoomed-in image of the icy object.
Source: HubbleSite News Center, Image ID: STScI-PRC02-17b, web-print.jpg
This drawing shows a method by which the passage of meteors can be observed using radio reflection techniques. The experimental setup consists of a sensitive receiver which is tuned to a distant broadcast station in the FM band. Due to the radio horizon, there is no signal received under normal circumstances. However, if a meteor enters the atmosphere, it leaves an ionized trail which can reflect the signal in the direction of the receiver's antenna. An incoming meteorite can therefore be associated with a sharp peak in the signal strength of the receiver.
Source: Astronomical Observatory of the University of Ghent, Automated Meteor Observations , Image ID: meteor1.gif
Meteor burst communications involves scattering VHF radio signals off the ionized trails left by meteors in the upper atmosphere. This form of communication has evolved from a curiosity noted by amateur radio enthusiasts to the point that meteor burst terminals are now commercially available and can be used to provide radio link connections beyond the horizon from remote locations that have little or no communications infrastructure. This image shows an oscilloscope trace of a radio frequency signal scattered from a meteor trail in a communications test.
Source: US Air Force Rome Laboratory, Advanced Meteor Burst Communications Facility, Image ID: meteorsc2.gif
The NASA spacecraft Deep Space One was designed as a test mission for lots of new technologies. In September of 2001, the spacecraft was aimed to fly towards the nucleus of a comet. The best-to-date images of a comet's nucleus are available here.
Source: NASA Jet Propulsion Laboratory, Deep Space 1 -- Comet Borrelly Flyby, Image ID: borrelly_1.jpg
This image shows the nucleus of Halley as observed by the Giotto spacecraft on March 13, 1986. Jets of material can be seen originating from two regions on the nucleus. The mission was named Giotto after the Italian painter Giotto di Bondone, who depicted comet Halley on one of his frescoes in the Scrovegni chapel in Padua in 1304. The spacecraft encountered Halley at a distance of 0.89 A.U. from the Sun and 0.98 A.U. from Earth while moving at a spacecraft trajectory angle of 107 degrees from the cometsun line. The goal was to come within 500 km of the comet at closest encounter. The actual closest approach was measured at 596 km. This is a composite image assembled from a series of smaller pictures sent by the spacecraft shortly before its camera was disabled by an encounter with cometary debris just before its closest approach.
Source: National Space Science Data Center, Comet Fact Sheet, Image ID: giotto_halley.jpg
A series of images of Comet 1995 O1 (Hale-Bopp) through the standard filters B (Blue), V (Green-Yellow) and R (Red) was obtained with the MPI/ESO 2.2-m telescope in mid-May 1996. One of the R-images is reproduced here in false color enhancement to improve intensity contrast. The field of view shown here is 200 x 190 arcsec. North is up and east is to the left; 1 pixel = 0.336 arcsec. At the time of the exposure, the comet was about 573 million km from Earth and 661 million km from the Sun. In the sky, it was steadily moving north through the constellation of Sagittarius.
Source: European Southern Observatory, Images of Comet Hale-Bopp (May 14, 1996), Image ID: Press Photo 29a/96
A NASA Hubble Space Telescope image of approximately 20 objects that comprised the multiple nuclei of comet P/Shoemaker-Levy 9, giving it the appearance of a "string of pearls." The various pieces of this comet collided with the planet Jupiter in July 1994. Before collision, the nuclei were probably less than 5 kilometers across each. This image was taken with the HST Wide Field and Planetary Camera on July 1, 1993.
Source: National Space Science Data Center, SL9 Pre-Impact Images, Image ID: sl9hst.gif