After several delays in recent months, NASA is set to launch the space probe Dawn on Thursday 7:20 a.m. EDT on an eight-year mission to unlock the secrets of the solar system and how it was born. Dawn is scheduled to enter orbit around asteroid Vesta in October 2011, and then begin orbiting dwarf planet Ceres in February 2015.
Dawn Mission Home Page
Kategorie: Asteroiden & Co.
Large Asteroid Breakup May Have Caused Mass Extinction On Earth
The impactor believed to have wiped out the dinosaurs and other life forms on Earth some 65 million years ago has been traced back to a breakup event in the main asteroid belt. A joint U.S.-Czech team from Southwest Research Institute (SwRI) and Charles University in Prague suggests that the parent object of asteroid 298 Baptistina disrupted when it was hit by another large asteroid, creating numerous large fragments that would later create the Chicxulub crater on the Yucatan Peninsula as well as the prominent Tycho crater found on the Moon.
Southwest Research Institute News
Abstract: An asteroid breakup 160 Myr ago as the probable source of the K/T impactor
Baptistina asteroid family
(PDF from the 2007 meeting of the Lunar and Planetary Institute)
Crystals On Meteorite Reveal Clues To Early Solar System Evolution
A new study has uncovered tiny zircon crystals in a meteorite originating from Vesta (a large asteroid between Mars and Jupiter), shedding light on the formation of planetesimals (small astronomical objects that form the basis of planets). To date, studying zircons in eucrites – meteorites formed by volcanic activity – has been difficult due to impact-induced fracturing and their small size; typically less than five microns. Most eucrites are formed within the asteroid belt that orbits between Mars and Jupiter, a heap of astronomical debris from the earliest epoch of the solar system. In a study published in the recent issue of „Science“, researchers collected samples from eucrites found in Antarctica believed to have originated from Vesta. The researchers used new technology to reveal that asteroid’s boiling rock turned solid and crystallized within less than 10 million years of solar system formation.
University of Toronto: Crystals on meteorite hold a key to understanding building blocks of planets
Could a crater solve the 1908 meteor mystery?
In late June of 1908, a fireball exploded above the remote Russian forests of Tunguska, Siberia, flattening more than 800 square miles of trees. Researchers think a meteor was responsible for the devastation, but neither its fragments nor any impact craters have been discovered so far. Italian researchers now think they’ve found a smoking gun: the 164-foot-deep Lake Cheko, located just 5 miles northwest of the epicenter of destruction.
Hubble photographs two huge asteroids
The Hubble Space Telescope has imaged two of the largest known asteroids, revealing craters and other features that will soon be the targets of close-up observations by NASA’s Dawn spacecraft.
Hubble Images of Asteroids Help Astronomers Prepare for Spacecraft Visit
Scientists find a solar-powered asteroid
An international research team led by Academy Research Fellow Mikko Kaasalainen from the University of Helsinki has found an asteroid whose rotation receives an extra kick from solar radiation. Asteroid 1862 Apollo’s diameter is about 1,5 km, it has a small moonlet, and its orbit crosses that of the Earth. The team reconstructed Apollo’s shape and determined its rotational state using brightness measurements from several years. They found that Apollo’s rotation speed steadily increases, and showed that this is due to the re-radiation of solar energy from its surface. The study is published online in „Nature“.
Acceleration of the rotation of asteroid 1862 Apollo by radiation torques
Lutetia asteroid in Rosetta’s spotlight
Earlier this month ESA’s Rosetta spacecraft had a first look at asteroid 21-Lutetia, one of the targets of its long mission. The onboard camera OSIRIS imaged the asteroid passing through its field of view during the spacecraft’s gradual approach to Mars. The planet will be reached on February 25, 2007, for the mission’s next gravity assist.
https://www.esa.int/Science_Exploration/Space_Science/Rosetta/Lutetia_asteroid_in_Rosetta_s_spotlight
Schwarzer Diamant aus dem All?
Kohlschwarze Diamanten stammen nicht aus dem Schoß der Erde, sondern aus dem Weltraum. Diese Vermutung bekräftigen neue Messungen amerikanischer Geowissenschaftler. In vielerlei Hinsicht ähnelt die Zusammensetzung der „Carbonados“ demnach der von Diamanten, wie sie in Meteoriten gefunden und im All beobachtet worden sind. Carbonados fand man bislang nur in Brasilien und Zentralafrika. Anders als „normale“ Diamanten, sind sie undurchsichtig und porös, weisen eine matte Oberfläche auf und erinnern insgesamt eher an Koks. Schon ihr Gehalt an metallischen Spurenelementen spreche gegen einen Ursprung im Erdmantel, erläutern die Forscher um Jozsef Garai von der Florida International University. Um mehr über den Aufbau der schwarzen Diamanten zu erfahren, bombardierten Garai und Kollegen vier Carbonados mit intensiver Infrarot-Strahlung. Frühere Untersuchungen dieser Art waren auf das Problem gestoßen, dass die Poren der Steine Silikatmineralien enthalten, welche ausgerechnet im besonders interessanten Wellenlängenbereich zwischen 7,7 und 10 Mikrometern absorbieren. Um diesen Störfaktor zu beseitigen, zermahlten die Forscher ihre Carbonados zunächst zu feinem Pulver, das sie mehrere Tage lang mit Salz- und Flusssäure behandelten. Wie die Gruppe in den „Astrophysical Journal Letters“ berichtet, enthält das Material sowohl Stickstoff als auch Wasserstoff in Form und Menge, wie es typisch für Diamanten aus dem All ist. Daher sei es denkbar, dass sich der Kohlenstoff der Carbonados in einer wasserstoffreichen Region im All zusammengelagert habe. Vermutlich seien die schwarzen Diamanten dann vor 2,6 bis 3,8 Milliarden Jahren mit Asteroiden auf die Erde gelangt.
Infrared Absorption Investigations Confirm the Extraterrestrial Origin of Carbonado-Diamonds
Ruby from a red giant
A speck of crystal that fell to Earth in a meteorite has been traced back to a red-giant star.
It’s not the same as having a sample return mission to, say, Aldebaran, but it’s still pretty awesome: mounted on a gold pedestal in a laboratory in the Carnegie Institute of Washington and then bombarded by ions, a grain of less than a micrometer has confessed that it came from a different star. According to research published in the December issue of „Astronomy & Astrophysics“, the crystal probably formed near a star of intermediate mass, 4 to 7 times that of our Sun, which was nearing the end of its life and had entered the red-giant stage. Lead author Maria Lugaro, an Italian astronomer at Utrecht University in the Netherlands, says finding and analyzing similar specks could yield important information about the conditions inside red giants. The speck in question has been christened OC2. No one knows precisely how it got to Earth. It was found in residue left after pieces of three stony meteorites (chondrites) were dissolved in acid to analyze their contents.
https://astronomy.com/News-Observing/News/2006/12/Ruby%20from%20a%20red%20giant.aspx
Organic Material Found in an Ancient Meteorite
NASA researchers have discovered organic material inside a meteorite that recently fell in Canada’s Tagish Lake. The meteorite is especially valuable because scientists collected it shortly after it crashed in 2000, ensuring it wasn’t contaminated by local bacteria. The meteorite seems to contain many small hollow organic globules, which probably formed in the cold molecular cloud of gas and dust that gave birth to the Solar System. Meteorites like this have been falling to Earth for billions of years, and probably seeded the early planet with organic material.
Carbon globules in meteorite may have seeded Earth life