Category: Asteroids

Asteroid 10537 (1991 RY16) is a rarity. It is composed of basaltic rock (i.e. rock that cooled quickly after formation from a molten state) and appears to have evolved independently from the large asteroid Vesta. Vesta suffered a huge impact billions of years ago, and the debris from this collision litters the inner asteroid belt. These “Vestoids” make up the majority of the basaltic asteroids apart from three known isolated bodies including asteroid 1991 RY16. Scientists are therefore very interested to understand the evolution of 1991 RY16, possibly helping us understand the formation of the Solar System and why there aren’t more basaltic asteroids out there…

The asteroid belt occupies the volume of space roughly between the orbits of Mars and Jupiter. There are thousands of known rocky bodies in the belt, but half of the mass can be found in four major asteroids; Ceres, 4 Vesta, 2 Pallas, and 10 Hygiea. Ceres is actually classified as a minor (or dwarf-) planet as it is over 900km (560 miles) in diameter and is roughly spherical, unlike other asteroids that are irregular in shape. Large asteroid Vesta suffered a huge impact during the formation of the Solar System some 3.5 billion years ago and the debris (about 1% of its total mass) from this collision can be found scattered around the orbit of Vesta (~2.4 AU). These Vestoids usually explain many of the basaltic asteroids in this region of the asteroid belt.

So where does 1991 RY16 come in? Researchers at the Institute for Astronomy (IfA), University of Hawaii, carried out an analysis of the object after a previous study that utilized the Sloan Digital Sky Survey Moving Object Catalog. The IfA astronomers then used optical and near-infrared observations to derive spectroscopic data for 1991 RY16 to see whether it can be related to any of the asteroid groups in the asteroid belt. It turns out that its basaltic surface composition doesn’t appear to match up with any of the large groups of asteroids, and if its orbital radius is worked into the equation, it is highly unlikely that it could have travelled from any of the groups. 1991 RY16 appears to be an asteroid loner… or does it?

Firstly, the 5-15 km wide asteroid had to be ruled out from being a more common Vestoid. For a start 1991 RY16 isn’t even a remotely close spectroscopic match to any of the known Vestoids. Its orbit beyond the 3:1 Jupiter orbital resonance (at a distance of 2.5 AU) suggests that it could not have travelled from 2.4 AU, through the resonance and to its present orbit of 2.85 AU. The orbital resonances of the larger planets cause separation in the asteroid belt populations, confining them to their orbits. So, 1991 RY16 doesn’t originate from the Vesta impact event 3.5 billion years ago. Looking at the positions of the known asteroids (chart pictured), the IfA group ruled out the association of 1991 RY16 with any of the neighbouring asteroid groups (such as Gefion and Eos) as there is little spectroscopic evidence and it isn’t possible that the asteroid simply drifted (even after considering the strange Yarkovsky effect that predicts small rocky bodies experience a small deflection in trajectory due to anisotropic emission of thermal photons).

The possible remaining explanation could lie with a large asteroid near the orbital vicinity of 1991 RY16. The spectroscopic analysis of 1991 RY16 reveals that it could be a large chunk from another, differentiated asteroid. Although more analysis is required, 349 Dembowska (of ~140km in diameter) could be the parent asteroid 1991 RY16 was chipped from during an impact in the young Solar System. The IfA researchers are keen to point out that more observations are required to see if there is any other debris from this possible collision matching the surface composition of 1991 RY16.

For more detail into this very interesting research, check out the paper below.

Source: “A Spectroscopically Unique Main Belt Asteroid: 10537 (1991 RY16)” (arXiv pdf)

When a large enough asteroid strikes the Earth, the devastation effects the entire globe. And the dinosaur-killing asteroid that smashed into the Yucatan peninsula 65 million years ago was no exception. According to researchers, just one outcome from the strike: carbon in the Earth’s crust was liquified and formed tiny beads that rained back down across the entire planet.

These beads are known to geologists as carbon cenospheres, and they’re produced during the burning of coal and crude oil. They’re a classic indicator of industrial activity. But 65 million years ago, there were no power plants, so scientists proposed that asteroid impact-driven forest fires could get hot enough to make them too.

As the asteroid struck, huge chunks of molten rock fell back to Earth, igniting forest fires across the planet. It’s here that scientists find evidence of charcoal from the fires, but not the cenospheres.

New evidence, reported in this month’s edition of the journal Geology, shows that natural fires can’t make the microscopic spheres.

Instead, the international team of researchers propose that they had to have been formed from an asteroid strike. A key additional piece of evidence is that the carbon cenospheres are deposited right next to a think layer of the element iridium.

It was this layer of iridium that helped to give scientists the evidence they needed to point to asteroids as the cause of the dinosaur extinction 65 million years ago. Since iridium is much more likely to be formed in the Solar System asteroids than in the Earth’s crust, a concentrated layer of the stuff had to come from off planet.

And the cenospheres have been discovered around the planet next to the iridium layer, in Canada, Spain, Denmark and New Zealand. The key discovery is that the cenospheres get smaller as you move away from the impact site. This matches the prediction that the heavier particles would rain back down to Earth closer to the impact, while the lightest particles would be carried across the entire planet.

The researchers were able to calculate the total amount of carbon injected into the atmosphere from an asteroid impact, and put the number at 900 trillion tonnes. This helps scientists get a better estimate of the impact size and damage.

Original Source: Indiana University

Way back in the beginning of the solar system, about 4.5 billion years ago, the first materials began to condense from gasses into solid particles. These materials were rich in calcium and aluminum. Astronomers have thought that at least some of the solar system’s oldest asteroids should have plenty of these two elements, but no asteroids had ever been found that were particularly rich in them. Until now. A team of scientists recently identified three previously unknown asteroids that appear to be among the oldest objects in our solar system.

Using visible and infrared data from telescopes on Mauna Kea in Hawaii, astronomers from the University of Maryland found asteroids that appear to relatively unchanged since they formed in the early stages of our solar system’s development. “We have identified asteroids that are not represented in our meteorite collection and which date from the earliest periods of the Solar System,” said research astronomer Jessica Sunshine. “These asteroids are prime candidates for future space missions that could collect and return samples to Earth, providing a more detailed understanding of the Solar System’s first few millions of years.”

Meteorites found on Earth do contain small amounts of calcium and aluminum. Called calcium aluminum inclusions (CAIs) these white, millimeter-sized objects are found in meteorites, often together with chondrules, which are small balls of iron or magnesium.

In 2002, an international team of scientists accurately dated CAIs at 4.57 billion years, making them the oldest known objects in the solar system. When the famous Allende meteorite was found in 1969, scientists first recognized these inclusions matched many properties expected to be found in the early solar system.

Sunshine’s team used the SpeX instrument at the NASA Infrared Telescope facility to look at the surface of asteroids, looking for “fingerprints” indicative of CAIs. Sunshine said that several asteroids have been found that contain 2-3 times more CAI materials than any known meteorite. “It appears ancient asteroids have indeed survived, and we know where they are,” she said.

Original news source: Eureka Alert

Yesterday we talked about the discovery of amino acids in meteorites. And then today comes news that there was an explosion of life (pardon the pun) after meteorites rained down more than 400 million years ago. Even though the Earth was struck by more than 100 1-km meteorites in a short period of time, life not only survived, it thrived.

The string of impacts occurred during the Ordovician period, between 490-440 million years ago. It wasn’t quite life as we know it, but creatures were living on land, and organisms had evolved to fit every niche in the oceans.

According to planetary scientists, a disruption in the asteroid belt about 470 million years ago sent hundreds of space rocks out of their normal orbit, and into ours.

Over a few million years, more than 100 separate meteorites larger than 1 km across struck the Earth, throwing up a Sun-clogging shroud of dust. Plants, starved for sunlight, died, and the chains of life depending on them collapsed.

But incredibly, life thrived after this period, evolving into new and interesting life forms.

Researchers from the University of Copenhagen and Lund University gathered together chemical samples from meteorites, fossils, and examined several craters in Sweden. The Lockne crater, for example, is located in northern Sweden and has a diameter of 7.5 km across.

They found evidence for the thriving life forms in layers newer than the ones containing debris from the meteorite strikes.

“You could say that biological evolution experienced a serious boost within a relatively short period of time. And, as is the case with, for example, volcanic eruptions or large forest fires, the impacts initially had a devastating effect on all life, but from the ashes arose a much richer fauna than had existed previously,” said Dave Harper from the University of Copenhagen.

This is research we’ve seen before. Paleontologists announced earlier this year that life can bounce back quickly from an extinction event, but it takes a long time for the true diversity of life to reappear. So, after most life is wiped out by an asteroid, the cockroaches and rats take over. You might have the same number of creatures, but it takes many years before you get rich ecosystems with butterflies and giraffes too.

Original Source: Nature Geoscience