Between the 26th and 28th of June, Unicamp will receive renowned foreign researchers in the area of planetary sciences for the workshop Impact Processes as a Path to Habitability of Planetary Bodiess (impact processes as a path to the habitability of planetary bodies). It will discuss the most recent advances in understanding the role of cosmic impact processes for the development of life on icy and rocky planetary bodies. Such impacts are among the main geological processes that can lead to the establishment of conditions for this celestial body to be habitable. The event is coordinated by the professor at the Geosciences Institute (IG) at Unicamp Alvaro Crósta, by the researcher at the Jet Propulsion Laboratory (JPL-Nasa/Caltech, USA) Rosaly Lopes and by the professor at the University of Western Ontario (Canada) Catherine Neish with the support from Unicamp and the São Paulo State Research Support Foundation (Fapesp).
Crósta is dedicated to studying the formation of craters resulting from meteoritic impacts and is part of the macroproject “Habitability of worlds with hydrocarbons: Titan and beyond”, coordinated by Lopes, a Brazilian researcher who has worked at NASA for more than three decades and is part of the virtual research network NASA Astrobiology Institutes (NAI). Since 2018, the Unicamp professor has been researching such impact processes on Titan, Saturn's largest moon, through the analysis of data collected by Cassini-Huygens mission. The macro project brings together scientists from different parts of the world who meet periodically in different locations to discuss the results obtained and plan the next steps.
According to the teacher, in the workshop, which will take place almost entirely in person at Unicamp, “the researchers will focus on the role of the impact processes of large asteroids capable of breaking icy crusts such as that of Titan and other satellites that have an icy crust covering liquid oceans. The objective is to look for evidence of habitable environments, that is, places with conditions favorable to the development of life on these planetary bodies that have in common a crust formed by ice and the presence of frozen oceans in the subsurface, also called oceanic worlds.” Crósta states that these oceans have potential conditions for the emergence of life (including the presence of basic compounds).
In addition to Crósta, the guest speakers are the aforementioned Lopes and Neish, Michael Malaska (JPL-Nasa/Caltech), Ralph Lorenz (Johns Hopkins University/Applied Physics Laboratory) and Veronica Bray (University of Arizona). “The selection of guest speakers was based on the fact that they were leaders in certain research topics related to the general theme of the workshop”, says the Unicamp professor. Other participants include project leaders at their workplaces, postgraduate students from the USA, Canada and the Netherlands, USP (University of São Paulo) and UFRJ (Federal University of Rio de Janeiro) and professors from other universities Brazilians. “This is a very current research topic and I believe this is the first event of this nature in Brazil”, he notes. “This is cutting-edge science, both here and around the world. So, it is very important that Brazil hosts advanced science events like this, even more so in an area like planetary geology, whose development is still incipient in our country”, he celebrates.
Field activity
Once the workshop at Unicamp, part of the group will visit the meteorite impact craters of Vargeão and Vista Alegre, in the southern region of Brazil. “These are rare geological structures formed in volcanic rocks of basaltic composition that, by analogy, are important for understanding impact processes on rocky bodies such as Mars, Venus and the Moon, where similar rocks occur”, explains Crósta. The teacher explains that there are three craters in Brazil formed in basalt and one in India, but the latter is filled with a lake. There are around 200 craters on Earth proven to be created by meteorite impacts, 9 of which are in Brazil – all of which were identified by Crósta over more than four decades of research.
Among the rock samples linked to impact processes that the professor has in his collection, collected in craters in Brazil and also in other countries, he displays a shatter cone, a rock with a striated conical shape, formed in basalt. “This structure is diagnostic of the occurrence of a meteorite impact. They are extremely rare and those that were formed in basalt are only known in Brazil, precisely in the two craters that will be visited”, he explains. With a three-dimensional shape, the specimen collected in Vargeão was formed in a natural fracture. “When broken with a hammer, the rock opens naturally along the striated conical surface and it is possible to visualize the mold and counter-mold – as if it were a fossil”, he says.
From a laboratory analysis, it is possible to know that this rock was subjected to extremely high pressures, pressures that are not produced by any other process that occurs in the Earth's crust, only in the mantle. “There is only one man-made process that can reach pressures similar to those generated by meteoritic impacts, and that process is the explosion of nuclear devices. At the atomic bomb test sites in the State of Nevada, USA, there are structures similar to shatter cones, but well located at the point where the explosion occurs”, explains the teacher. The propagation of the shock waves in Vargeão occurred for several kilometers around the point of impact, and may have formed shatter cones and other types of shock deformation over relatively large areas. According to the Unicamp researcher, the specimen in the IG must have formed 500 m deep and, with the movement of the crust, rose to the surface within a few seconds after the meteor impact. “These deformed rocks serve as a model for studying other planets that have similar rocks, such as Mars, where basalts are common,” he explains. This is what the participants of the workshop want to see on-site visit.
