Ancient Asteroids Research Articles

Diamonds in the rubble

Two ancient asteroids with distinctive diamond-like shapes are revealing clues not only about their own formation, but that of the solar system as well. For the past three years, two spacecraft have been studying a pair of the most primitive solar system objects ever explored. The asteroids, Ryugu and Bennu, born of violent collisions in the asteroid belt, are some of the smallest objects ever visited by spacecraft. Ryugu is just over a kilometer across, and Bennu is about half as wide. The asteroid Bennu ejects particles from its surface in January 2019—a phenomenon captured in an image composed from multiple photos. Image credit: NASA/Goddard/University of Arizona/Lockheed Martin. But these small bodies are promising a huge bounty of data to astronomers over the next few years. Although the findings could revolutionize our understanding of the history, formation, and composition of asteroids, they may also tell us a little about the solar system during its infancy. That’s because these carbon-rich (1) asteroids, with their coal-dark surfaces, are also among the darkest bodies known in the solar system. Although that can make it difficult to observe them from Earth, studying them could tell us about the building blocks of life that such asteroids may have delivered to Earth early in the history of the solar system. Before researchers could hope to study these asteroids, they first had to reach them. This, by itself, was an enormous challenge. Only a handful of spacecraft have visited asteroids, and fewer still have managed to orbit one of these tiny, irregularly shaped objects. The Hayabusa spacecraft, launched by the Japanese Aerospace Exploration Agency (JAXA) in 2003, became the first to collect a sample of an asteroid. But the mission was beset by engine problems. Hayabusa’s prospects for returning with a sample remained uncertain for much of …

Veil of dust from ancient asteroid breakup may have cooled Earth

Veil of dust from ancient asteroid breakup may have cooled Earth

Japanese rover lands on ancient asteroid for 16-hour mission

Third lander from Hayabusa2 has less than a day to collect data before its battery runs out. The shoe-boxed sized lander from Hayabusa2 has less than a day to complete its mission before its battery runs out.

Vortex magnetic structure in framboidal magnetite reveals existence of water droplets in an ancient asteroid

The majority of water has vanished from modern meteorites, yet there remain signatures of water on ancient asteroids. How and when water disappeared from the asteroids is important, because the final fluid-concentrated chemical species played critical roles in the early evolution of organics and in the final minerals in meteorites. Here we show evidence of vestigial traces of water based on a nanometre-scale palaeomagnetic method, applying electron holography to the framboids in the Tagish Lake meteorite. The framboids are colloidal crystals composed of three-dimensionally ordered magnetite nanoparticles and therefore are only able to form against the repulsive force induced by the surface charge of the magnetite as a water droplet parches in microgravity. We demonstrate that the magnetites have a flux closure vortex structure, a unique magnetic configuration in nature that permits the formation of colloidal crystals just before exhaustion of water from a local system within a hydrous asteroid.

Ancient asteroids kept on coming

Ancient asteroids kept on coming

Pyrolysis and mass spectrometry studies of meteoritic organic matter

Meteorites are fragments of extraterrestrial materials that fall to the Earth's surface. The carbon-rich meteorites are derived from ancient asteroids that have remained relatively unprocessed since the formation of the Solar System 4.56 billion years ago. They contain a variety of extraterrestrial organic molecules that are a record of chemical evolution in the early Solar System and subsequent aqueous and thermal processes on their parent bodies. The major organic component (>70%) is a macromolecular material that resists straightforward solvent extraction. In response to its intractable nature, the most common means of investigating this exotic material involves a combination of thermal decomposition (pyrolysis) and mass spectrometry. Recently the approach has also been used to explore controversial claims of organic matter in meteorites from Mars. This review summarizes the pyrolysis data obtained from meteorites and outlines key interpretations.

Re-evaluation of the Devonian family Helianthasteridae Gregory, 1899 (Asteroidea: Echinodermata)

Because of their taxonomic and morphologic diversity, the asteroids of the Lower Devonian Hunsruck Slate of Germany are important to both an understanding of the history of the class Asteroidea and to the interpretation of community evolution during the Paleozoic. Helianthaster Roemer, 1863, a large multiarmed Hunsruck asteroid, is redescribed. The Helianthasteridae Gregory is restricted to Helianthaster and Arkonaster Kesling, 1982 (Middle Devonian, Canada); Lepidasterella Schuchert is similar to the other two genera but known specimens are of poor quality and as a result the status of the genus is uncertain. Helianthaster is noteworthy in part because its size, multiarmed state, and presence of pedicellariae suggest certain crown-group genera, yet aspects of the arrangement of the ambulacral column are characteristic of the Paleozoic asteroid evolutionary grade. Neither Helianthaster nor other Hunsruck asteroids appear closely linked to the crown group; instead, functional patterns apparently re-emerged through time, although identification of specific behavior of ancient asteroids is difficult to impossible.

Response to Comment on "Ancient Asteroids Enriched in Refractory Inclusions"

Although the exact abundance of phases in carbonaceous chondrites remains debatable, a potentially lower absolute abundance of calcium- and aluminum-rich inclusions (CAIs) in the Allende meteorite does not change our fundamental conclusion. In a relative comparison, CAI-rich asteroids contain two to three times as many CAIs as the most CAI-rich meteorites. These asteroids are therefore greatly enriched in the earliest solar system materials and remain enticing targets for future exploration.

Comment on "Ancient Asteroids Enriched in Refractory Inclusions"

Sunshine et al. (Reports, 25 April 2008, p. 514) reported that certain asteroids contain 30 +/- 10 volume percent calcium- and aluminum-rich inclusions (CAIs). We contend that the amount of CAIs in CV chondrites is two to three times as low as the 10 volume percent assumed by the authors; thus, we question whether the CAI-rich bodies they studied are indeed older than known asteroids or formed before the injection of (26)Al into the solar nebula.

How to detect another 10 trillion small Main Belt asteroids

Estimates of the size distribution of Main Belt asteroids suggest that there is an undetected population of approximately 10 trillion objects in the meter-to kilometer-range. These small objects are highly diverse impact generated fragments of ancient asteroids. This vast and so far unexplored resource of small bodies holds a rich variety of information on the origin and evolution of our Solar System. Current Earth-based telescopes have, with a few exceptions, not been able to detect the faint and distant meter-sized asteroids in the Main Belt. Deep exposures cannot be used, unless the object can be tracked, which is not possible for an object in an unknown orbit. Small asteroids can be observed close up from a spacecraft but, so far, missions to the Main Belt have not had the ability to detect new small asteroids (with the exception of Dactyl, the kilometer-sized asteroid, that was found orbiting the much larger asteroid Ida). Due to the rapidly changing geometry, small asteroids can only be observed from a spacecraft for a very limited time, hence it is not possible to operate a spacecraft from the distant Earth and a fully autonomous mission is required. The technology required to build such spacecrafts does exist and has been tested in space. We have explored the scientific potential of deep space missions to detect and study small asteroids from spacecrafts traveling through the asteroid Main Belt.

Identifying ancient asteroids

Identifying ancient asteroids

Identifying Ancient Asteroids

Identifying Ancient Asteroids

Organic matter in carbonaceous meteorites: past, present and future research

Carbonaceous meteorites are fragments of ancient asteroids that have remained relatively unprocessed since the formation of the Solar System. These carbon-rich objects provide a record of prebiotic chemical evolution and a window on the early Solar System. Many compound classes are present reflecting a rich organic chemical environment during the formation of the planets. Recent theories suggest that similar extraterrestrial organic mixtures may have acted as the starting materials for life on Earth.

The origin and evolution of stony meteorites

The origin of stony meteorites landing on Earth today is directly linked to the history of the main belt, which evolved both through collisional evolution and dynamical evolution/depletion. In this paper, we focus our attention on the main belt dynamical evolution scenario discussed in Petit et al. (2001). According to Petit et al., during the planet formation epoch, the primordial main belt contained several Earth masses of material, enough to allow the asteroids to accrete on relatively short timescales.After a few My, the accretion of planetary embryos in the main belt zone dynamically stirred the remaining planetesimals to high enough velocities to initiate fragmentation. After a short interval, perhaps as long as 10 My, the primordial main belt was dynamically depleted of % of its material via the combined perturbations of the planetary embryos and a newly-formed Jupiter. The small percentage of objects that survived in the main belt zone became the asteroid belt. It has been shown that the wavy-shaped size-frequency distribution of the main belt is a “fossil” left over from this violent period (Bottke et al. 2004).Using a collisional/dynamical model of this scenario, we tracked the evolution of stony meteoroids produced by catastrophic disruption events over the last several Gy. We show that most stony meteoroids are a byproduct of a collisional cascade derived from large and ancient asteroid families or smaller, more recent breakup events. The meteoroids are then delivered to Earth by drifting in semimajor axis via Yarkovsky thermal drag forces until they reach a resonance powerful enough to place them on an Earth-crossing orbit.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Organic matter in ancient meteorites

The carbonaceous chondrites are fragments of ancient asteroids that have remained relatively unprocessed since the formation of the solar system 4.56 billion years ago. These carbon-rich meteorites contain a variety of extraterrestrial organic molecules that are a record of chemical evolution in the early solar system and subsequent aqueous and thermal processes on asteroids. Recent theories suggest that similar extraterrestrial organic mixtures may have acted as the starting materials for life on Earth.

Recent Origin of the Solar System Dust Bands

Infrared Astronomical Satellite (IRAS) observations in 1983 revealed the existence of several solar system dust bands. These dust bands are believed to be debris produced by recent disruption events among main-belt asteroids, particularly because dust particles have short dynamical and collisional lifetimes. Using young asteroid families as tracers of recent disruptions in the main belt, we linked the most prominent IRAS dust bands with their sources. We propose that the source regions of the dust bands with inclination 935 and 21 are the Veritas asteroid family at 3.17 AU and the Karin cluster located inside the Koronis asteroid family at 2.865 AU, respectively. The Veritas family and the Karin cluster formed by collisional disruptions of their ~140 and ~25 km diameter parent bodies at 8.3 ± 0.5 and 5.8 ± 0.2 Myr ago, respectively. Asteroid material from the former source may represent about one-quarter of the interplanetary dust particles that have been collected in the Earth's stratosphere (and that have been extensively studied in laboratories). We were unable to identify a recent collision in the main-belt region that could be responsible for the 14 IRAS dust band. The region of the Themis family remains the best candidate for this dust band. We speculate that the (4652) Iannini cluster (≲5 Myr old, ~12° inclination) is the source for the J/K dust band and that the (1521) Seinajoki cluster (~15° inclination) is the ultimate source for the M/N dust band. We point out that the dust bands' spatial distributions are consistent with our proposed sources. This, and the fact that many prominent but ancient asteroid families have no associated dust bands, strongly suggests that dust bands are primarily by-products of recent asteroid breakup events that occur throughout the main belt.