Nav: Home

Uncovering the hidden history of a giant asteroid

June 11, 2019

A massive 'hit-and-run' collision profoundly impacted the evolutionary history of Vesta, the brightest asteroid visible from Earth. This finding, by a team of researchers from Tokyo Institute of Technology, Japan's National Institute of Polar Research and ETH Zurich, Switzerland, deepens our understanding of protoplanet formation more than 4.5 billion years ago, in the early infancy of the Solar System.

In a remarkable feat of astronomical detective work, scientists have determined the precise timing of a large-scale collision on Vesta that helps explain the asteroid's lopsided shape. Their study, published in Nature Geoscience, pinpoints the collision to 4,525.4 million years ago.

Vesta, the second largest body in the asteroid belt, is of immense interest to scientists investigating the origin and formation of planets. Unlike most asteroids, it has kept its original, differentiated structure, meaning it has a crust, mantle and metallic core, much like Earth.

Most of what we know about the asteroid had so far come from howardite-eucrite-diogenite (HED) meteorites, following studies in the 1970s that first proposed Vesta as the parent body of these meteorites. In recent years, NASA's Dawn mission, which orbited Vesta in 2011-2012, reinforced the idea that HED meteorites originate from Vesta and provided more insights into the asteroid's composition and structure. Careful mapping of Vesta's geology revealed an unusually thick crust at the asteroid's south pole.

The new study provides a confident framework for understanding Vesta's geological timeline, including the massive collision that caused the formation of the thick crust.

Key to uncovering this timeline was examining a rare mineral called zircon found in mesosiderites (stony-iron meteorites that are similar to HED meteorites in terms of texture and composition). Based on a strong premise that both types of meteorites came from the same parent body, Vesta, the team focused on dating zircon from mesosiderites with unprecedented precision.

Makiko Haba of Tokyo Institute of Technology (Tokyo Tech), a specialist in geochemical and chronological studies of meteorites, and Akira Yamaguchi of Japan's National Institute of Polar Research (NIPR) were involved in sample preparation -- a major challenge, Haba explains, as fewer than ten zircon grains have been reported over the past few decades. "We developed how to find zircon in mesosiderites and eventually prepared enough grains for this study," she says.

Joining forces with co-authors at ETH Zurich who developed a technique to measure the age of the samples using uranium-lead dating, the team pooled their expertise to propose a new evolutionary model for Vesta. "This work could not be achieved without collaboration between Tokyo Tech, NIPR, and ETH Zurich," Haba points out.

The team highlights two significant time-points: initial crust formation 4,558.5 ± 2.1 million years ago and metal-silicate mixing by the hit-and-run collision at 4,525.39 ± 0.85 million years ago. This collision, impacting Vesta's northern hemisphere as shown in Figure 1, likely caused the thick crust observed by the Dawn mission, and supports the view that Vesta is the parent body of mesosiderites and HED meteorites.

By building on this study, Haba says she plans to examine "more precise conditions, such as temperature and cooling rate during and after the large-scale collision on Vesta based on mesosiderite and HED meteorite measurements."

"I'd like to draw a picture that shows the whole history of Vesta from the cradle to the grave," she says. "Combining such information with an impact simulation study would contribute to a more comprehensive understanding of large-scale collisions on protoplanets."

The dating method could be applied to other meteorites in future. Haba adds: "This is very important for understanding when and how protoplanets formed and grew to become planets like Earth. I'd like to also apply our dating method to samples from future spacecraft missions."

Tokyo Institute of Technology

Related Asteroid Articles:

Queen's University scientist warns of asteroid danger
A leading astrophysicist from Queen's University Belfast has warned that an asteroid strike is just a matter of time.
New study ranks hazardous asteroid effects from least to most destructive
If an asteroid struck Earth, which of its effects -- scorching heat, flying debris, towering tsunamis -- would claim the most lives?
Wrong-way asteroid plays 'chicken' with Jupiter
For at least a million years, an asteroid orbiting the 'wrong' way around the sun has been playing a cosmic game of chicken with giant Jupiter and with about 6,000 other asteroids sharing the giant planet's space, says a report published in the latest issue of Nature.
Ceres hosts organic compounds, and they formed on the asteroid, not beyond
Aliphatic organic compounds -- carbon-based building blocks that may have a role in the chemistry that creates life -- have been detected for the first time on Ceres, an asteroid and dwarf planet, a new study reveals.
It's a bird... It's a plane... It's the tiniest asteroid!
A team led by UA astronomer Vishnu Reddy has characterized the smallest known asteroid using Earth-based telescopes.
NASA to map Asteroid Bennu from the ground up
The OSIRIS-REx Laser Altimeter, or OLA will be used to create three-dimensional global topographic maps of Bennu and local maps of candidate sample sites.
NASA to map the surface of an asteroid
NASA's OSIRIS-REx spacecraft will travel to near-Earth asteroid Bennu to sample surface material and return it to Earth for study.
NASA instrument to use X-rays to map an asteroid
NASA's OSIRIS-REx spacecraft will launch September 2016 and travel to the near-Earth asteroid Bennu to harvest a sample of surface material and return it to Earth for study.
New type of meteorite linked to ancient asteroid collision
An ancient space rock discovered in a Swedish quarry is a type of meteorite never before found on Earth, and likely a remnant of a massive asteroid collision 470 million years ago that sent debris raining to Earth.
Scientists reconstruct the history of asteroid collisions
An international study, in which Spain's National Research Council (CSIC) participates, reveals that asteroids have endured a multitude of impact strikes since their formation 4,565 million years ago.

Related Asteroid Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...