Viranga Perera

Postdoc at the Johns Hopkins University Applied Physics Lab



My planetary science research involves computer modeling of granular material on asteroids. Granular material, like sand, can act both like a solid (you can make a pile of sand) and a liquid (sand flows inside an hourglass). The reason for studying granular material in the context of asteroids is that most asteroids are likely rubble-pile objects (i.e. they are gravitationally bound collections of smaller objects) and behave like granular material do. I run computer simulations that are similar to the simple example shown above of a collection of smaller particles falling towards the center due to gravity. Though not exactly like a real asteroid, the end product is similar to an asteroid in that it is made of a collection of smaller objects and thus allows me to study both surface and internal properties of asteroids. Real asteroids are not that spherical and are not made of smaller perfect spherical objects. However, in order to make these simulations more realistic the code that I am using not only incorporates gravity, but also friction (which is important since a ball rolling on a surface will not roll forever) and loss of energy due to collisions (since a ball that is dropped on the floor will not keep bouncing forever). The addition of certain physical aspects to these simulations make them more realistic. However, nothing beats actually visiting asteroids to collect data firsthand but space missions are expensive and visiting the large collection of known asteroids is not practical. Therefore, these simulations help us get a better sense of what the surfaces and interiors of asteroids are like. Hopefully, we will be able to verify these simulations in the future with more data from spacecraft that venture to asteroids.




    I am currently analyzing student data generated by the Habitable Worlds online science course offered by Arizona State University. Habitable Worlds is built on the Smart Sparrow architecture and is an adaptive learning environment that aims to help students learn by asking them to tackle one of humanities biggest questions: are we alone in the universe? The course helps students understand fundamental scientific concepts as they work through the Drake equation.

    By studying the data generated by this course, we can improve future offerings of the course by making adjustments that help students learn the subject matter in a more effective manner. Furthermore, we can search for insights that help improve the emerging sector of online education.


     The Moon's nearside is shown on the left and the farside is shown on the right

    The Moon's nearside is shown on the left and the farside is shown on the right

    At UC Santa Cruz, I worked on the lunar asymmetry problem (see Our 2011 LPSC abstract). Due to the fact that the Moon is tidally locked we can only see the nearside of the Moon from the Earth while the farside of the Moon faces away from us. It has been long known that the nearside and the farside of the Moon are geologically distinct. The darker areas (the result of ancient volcanism) and certain interesting chemical elements such as thorium are concentrated on the nearside. On the other hand, the farside topography is on average higher and the crustal thickness on the farside is on average greater than the nearside. Even though these features have been observed for a long time there has not been a comprehensive explanation as to why the Moon is asymmetric.

    While looking at the topography more closely, my adviser and I found that the geophysical asymmetries (particularly the topographic asymmetry) of the Moon might not be as fundamental as once thought. Even though today the Moon is topographically asymmetric, it still holds clues allowing us to infer the past symmetric shape of the Moon (see Our 2014 Nature publication).