An iron-clad asteroid

February 28, 2020

Itokawa would normally be a fairly average near-Earth asteroid - a rocky mass measuring only a few hundred metres in diameter, which orbits the sun amid countless other celestial bodies and repeatedly crosses the orbit of the Earth. But there is one fact that sets Itokawa apart: in 2005 it became a visit from Earth. The Japanese space agency JAXA sent the Hayabusa probe to Itokawa, which collected soil samples and brought them safely back to Earth - for the first time in the history of space travel. This valuable cargo arrived in 2010 and since then, the samples have been the subject of intensive research.

A team from Japan and Jena has now succeeded in coaxing a previously undiscovered secret from some of these tiny sample particles: the surface of the dust grains is covered with tiny wafer-thin crystals of iron. This observation surprised Prof. Falko Langenhorst and Dr Dennis Harries of Friedrich Schiller University in Jena. After all, over the last 10 years, research teams all over the world have exhaustively studied the structure and chemical composition of the dust particles from Itokawa, and no one had noticed the iron 'whiskers'. It was only when Japanese researcher Dr Toru Matsumoto, who is spending a year as a visiting scientist with the Analytical Mineralogy group at the Institute of Geosciences in Jena, examined the particles with a transmission electron microscope that he was able to locate the crystals using high-resolution images.

Solar wind weathers celestial bodies

This discovery is exciting not only because the tiny iron 'whiskers' - which have since been shown on other particles from the asteroid as well - had previously been missed. Of particular interest is how they were formed. "These structures are the consequence of cosmic influences on the surface of the asteroid," explains Falko Langenhorst. In addition to rocks, high-energy particles from the solar wind also strike the asteroid's surface, thus weathering it. An important constituent of the asteroid is the mineral troilite, in which iron and sulphur are bound. "As a result of space weathering, the iron is released from the troilite and deposited on the surface in the form of the needles that have now been discovered," says the mineralogist Langenhorst. The sulphur from the iron sulphide then evaporates into the surrounding vacuum in the form of gaseous sulphur compounds.

From the size and number of the ice crystals detected, the researchers can also estimate how quickly the asteroid loses sulphur. "The process is incredibly fast from a cosmic perspective," explains Toru Matsumoto. The crystals he analysed are up to two-and-a-half micrometres long, which is around one-fiftieth of the thickness of a human hair. "The tiny whiskers have already reached these sizes after around 1,000 years," adds the researcher from Kyushu University in Fukuoka. Over the long term, the analysis of the ice crystals can be used to gain a better understanding of weathering processes on other celestial bodies as well, and to determine their age.

To this end, the researchers already have specific asteroids in their sights. NASA's OSIRIS-REx probe is currently preparing to take samples from asteroid Bennu, while JAXA's Hayabusa2 is already on its way back to Earth. The Japanese probe visited the Ryugu asteroid last year and, as with Itokawa, it collected dust particles. The samples should land on Earth at the end of 2020 and the international team of Jena mineralogists and Toru Matsumoto are awaiting them with anticipation.
-end-
Original publication:

Matsumoto T et al. Iron whiskers on asteroid Itokawa indicate sulfide destruction by space weathering. Nature Communications (2020), DOI: 10.1038/s41467-020-14758-3, https://www.nature.com/articles/s41467-020-14758-3

Contact:

Prof. Falko Langenhorst
Institute of Geosciences of Friedrich Schiller University, Jena
Carl-Zeiss-Promenade 10, 07745 Jena, Germany
Tel.: +49 (0)3641 / 948710 (Secr.)
E-mail: Falko.Langenhorst@uni-jena.de

Friedrich-Schiller-Universitaet Jena

Related Asteroid Articles from Brightsurf:

Asteroid's scars tell stories of its past
Asteroid Bennu, which was just sampled by NASA's OSIRIS-REx mission, only recently migrated into Earth's neighborhood, according to a detailed analysis of impact marks on boulders on its surface.

Asteroid Ryugu shaken by Hayabusa2's impactor
Professor ARAKAWA Masahiko (Graduate School of Science, Kobe University, Japan) and Hayabusa2 mission members discovered more than 200 boulders, which either newly appeared or moved as a result of the artificial impact crater created by the Japanese spacecraft's Small Carry-on Impactor.

Scientists peer inside an asteroid
New findings from NASA's OSIRIS-REx mission suggest that the interior of the asteroid Bennu could be weaker and less dense than its outer layers--like a crème-filled chocolate egg flying though space.

Designing better asteroid explorers
Recent NASA missions to asteroids have used robotic explorers to gather data about the early evolution of our Solar System, planet formation, and how life may have originated on Earth.

ATLAS telescope discovers first-of-its-kind asteroid
University of Hawai'i telescope discovers extraordinary asteroid with comet-like features that has researchers puzzled.

An iron-clad asteroid
Mineralogists from Jena and Japan discover a previously unknown phenomenon in soil samples from the asteroid 'Itokawa': the surface of the celestial body is covered with tiny hair-shaped iron crystals.

Asteroid impact enriches certain elements in seawater
University of Tsukuba researchers found two processes immediately after the end-Cretaceous asteroid impact that likely supplied chalcophile elements to the ocean, i.e., impact heating and acid rain.

Turbulent times revealed on Asteroid 4 Vesta
Planetary scientists at Curtin University have shed some light on the tumultuous early days of the largely preserved protoplanet Asteroid 4 Vesta, the second largest asteroid in our solar system.

In death of dinosaurs, it was all about the asteroid -- not volcanoes
Volcanic activity did not play a direct role in the mass extinction event that killed the dinosaurs, according to an international, Yale-led team of researchers.

Active asteroid unveils fireball identity
At around 1 a.m. local standard time on April 29, 2017, a fireball flew over Kyoto, Japan.

Read More: Asteroid News and Asteroid Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.