Brazil has a new meteorite. On September 18, 2020, a farmer from Tiros, in Minas Gerais, found a very different rock near a trail on his property. It was the newest meteorite discovered in Brazil, Meteorito Tiros. And this is not just any meteorite. It has a fantastic history from the moment it was formed until it entered the Earth’s atmosphere.
The history of this meteorite begins a long time ago, in one of the largest asteroids in the solar system: Vesta. About 1 billion years ago, a gigantic impact completely changed the surface of that asteroid, creating a 505 km crater and launching to space trillions of tons of rocks from surface, crust and even of mantle of Vesta.
The crater, called Rheasilvia, cover about 90% of the southern hemisphere of Vesta. Close to the South Pole, where the impact occurred, a peak over 22 km high was formed by the “rebound” effect of the impact. A series of troughs concentric to Rheasilvia can be found close to the asteroid’s equator and even a deformation in the crust on the opposite side of the crater may have been generated by the impact violence.
Vesta Asteroid and Rheasilvia Cratera – Credits: NASA/JPL
In space, the material ejected from this impact generated the Vesta Family of asteroids, which orbit the Sun inside the main belt. These asteroids are responsible for about 6% of the meteorites that fall on our planet and, among them, is one that hit Earth in the early hours of May 8, 2020, generating a beautiful meteor that scared several residents of some cities in Triângulo Mineiro and was recorded by eight Clima ao Vivo cameras in Minas Gerais, São Paulo and Paraná.
The May 7, 2020 night started quite foggy in the region of Patos de Minas in Minas Gerais. Arriving home in the afternoon, after a long day at work, Ivan Soares decided to leave to finish installing and configuring his system of meteor monitoring cameras the next day. Ivan is member of BRAMON, the Brazilian Meteor Observation Network and, after a system maintenance, tiredness and the bad wheather led him to leave to finish the process the next day. Turned off that night, their cameras failed to record one of the most impressive meteors in recent years in that region. This obviously frustrated him, but at the same time it motivated him to investigate the case thoroughly until he have in your hands the meteorite that falls that night.
At 03h25 in the dawn, on May 8th, after a billion years wandering through interplanetary space, the small fragment of rock coming from Vesta’s crust reached the Earth’s atmosphere over the State of Minas Gerais. The bolide was seen in several cities in Minas Gerais and São Paulo and residents in at least 18 cities in the Triângulo Mineiro report having heard a loud explosion noise. The fireball was recorded by eight Clima ao Vivo cameras from seven cities in Minas Gerais, São Paulo and Paraná. It was also filmed by the Sonsky Observatory’s allsky camera, an NTV surveillance camera and another on a farm in Patos de Minas. From space, the geostationary satellite GOES-16 detected the flash generated by the meteor on its GLM instrument, a device used to map lightning.
Trajectory and Strewn Field
From the analysis of the videos, BRAMON calculated the trajectory of the meteor through the atmosphere. The meteoroid reached the atmosphere at a very low inclination, approximately 15.8 ° in relation to the ground and covered a total of 180.1 kilometers in approximately 9.76 seconds, appearing between Uberaba and Araxá and becoming extinct at an altitude of 29, 7 kilometers, west of the Municipality of Tiros. The luminosity of the bolide indicates an initial mass of the meteoroid between 180 and 300 kg, with approximately 95% of this mass being vaporized by the heat generated in the atmospheric passage.
From this trajectory, the American engineer Jim Goodall, calculated a meteorite dispersion field covering a vast area about 7 kilometers wide, 84 kilometers long, between the municipalities of Tiros and Morada Nova de Minas.
Despite the possibility of having meteorites on the ground, the resulting mass was not very high, and the dispersion area was immense, covering a mountainous region and with great vegetation cover. The chances of finding something in the field were very small. Adding this to the fact that Brazil is facing a pandemic, it was preferred not to disclose the dispersion area to avoid an eventual hunt for meteorites, which could help to spread the virus.
Since then, efforts have focused on finding videos, collecting testimonies and refining the trajectory. Much of this work was carried out by Ivan Soares, who went on to conduct field searches in May, but without success.
The first found
Finding a meteorite in such a vast area would not be easy. But not all statistics are able to predict chance. And it was by chance that a fragment of that meteorite with about 400g fell right on the edge of a trail, on a farm in the Rural Zone of Tiros. And on the afternoon of September 18, the unusual aspect of that rock caught the attention of Mr. Titota, a farmer who rode his horse on the trail. That dark stone with a glassy glow would certainly please his wife, who liked to collect minerals. Then, the farmer marked the spot and returned on foot in the late afternoon to take the stone. But when he picked up the rock on the ground and looked closely, he soon realized that it was not an ordinary rock. It was an extraterrestrial rock, the Tiros Meteorite.
Titota made a video of the rock and sent it to Father José Luís. At the same time, Father remembered the bolide from 4 months ago and believed it was the resulting meteorite. He sent the video to journalist Sandro Barcelos who published a short video of the rock found on the website of Portal Tirense Notícias. The story spread quickly and, as he saw the video, Teresinha Souza, from Grupo Mulheres de Estrelas, quickly associated the meteorite with the May bolide, since the rock had been found very close to the end of the trajectory calculated by BRAMON. Three days later, on September 21, Elizabeth Zucolotto, curator of meteorites at the National Museum, arrived in Tiros to analyze the meteorite together with Diana Andrade (UFRJ), Teresinha Souza (Women of Stars) and Ivan Soares (BRAMON). That day, Ivan held, for the first time, the meteorite he worked so hard to find.
According to the analyzes already carried out at UFRJ, Meteorito Tiros is an eucrite achondrite. Eucrites are rocky meteorites from deep regions of the Asteroid Vesta crust. It is believed that a large part of the Eucrites were launched into space by a gigantic impact at the south pole of Vesta, also responsible for the creation of the Rheasilvia crater, proportionally one of the largest in the Solar System. The eucrite is the most common type of achondrites, that is, rocks that have undergone a process of fusion and recrystallization, and no longer have chondrules. They are very similar to basalts and terrestrial lavas, but, while terrestrial ones are dark, eucrites are much clearer, as they are rich in calcium. Another characteristic of eucrites is the glassy glow of the melting crust, something very striking in Tiros Meteorite.
Tiros Meteorite – Credits: Tirense Notícias
For the time being, there is only one piece since meteorite, the fragment with about 400g found by Mr. Titota. The classification and official registration of Tiros Meteorite still depends on a deposit of at least 20g in an institution like the National Museum, which has already been agreed with the owner of the meteorite.
Since the first images of the meteorite found in Tiros were released, the city has received people interested in looking for meteorites. Researchers, meteorite hunters, and amateur astronomers have been there, but so far they have found nothing. Normally, it is already difficult to find a meteorite, but in the case of Tiros, it is much more complicated. Mainly, for being a not very large mass spread over a gigantic area with rugged relief and a lot of vegetation cover. And to make matters worse, as a meteorite, the meteorite does not contain metals in its composition, that is, hunters will not be able to count on magnets and metal detectors to aid the search. The only way is to look visually, preferably in opposite side of sun, which can enhance the brightness of your crust.
It does not seem that it will be easy to find other fragments of Tiros Meteorite, but the search continues. Furthermore, we already know that chance cannot be overlooked. So, nothing prevents another meteorite like this from being on the side of a road or trail, waiting for someone with watchful eyes to find it. Meteorites like that of Tiros, carry material from an asteroid hundreds of millions of kilometers from Earth. They are like pieces of a puzzle that help us to understand not only the Asteroid Vesta, but the entire Solar System and the universe around us. They deserve to be found, studied and deserve to contribute to Brazilian science.
The history of Meteorito Tiros shows the importance of institutions working together for science. With more than 170 cameras spread all over Brazil, Clima ao Vivo, a private company, provided free images of the bolide, which were used to calculate the trajectory by BRAMON, a collaborative citizen science network. The videos of that meteor were widely disseminated and reached a huge number of people in the region. Thus, when the strange rock was found, it was quickly associated with the bolide. The meteorite’s origin was confirmed through the analysis of Elizabeth Zucolotto of the National Museum and UFRJ. We now hope that, with the dissemination of this history, new fragments can be found, and that they can make the municipality even better known and contribute to the development of Science in Brazil and in the world.