Viranga Perera

Postdoc at the Johns Hopkins University Applied Physics Lab




Current Research

Thermochemical Evolution of the Moon.png

Thermal and Chemical Evolution of the Moon

The Moon is thought to have formed about 4.5 billion years ago as a result of a giant impact between a Mars-sized planetary body and the early Earth. One of the consequences of that formation is that the Moon likely formed very hot, hot enough for most of the Moon to be molten lava. We call the past molten portion of the Moon the Lunar Magma Ocean. We have evidence for this past molten state of the Moon in the form of unique rock samples brought back by the Apollo missions.

Currently, I am developing a computer program that can model the cooling of the Lunar Magma Ocean. This computer program needs to incorporate certain physics principles since it needs to model the correct heat loss through the modeled lunar surface. It also needs to include chemistry since it needs to calculate when solids (minerals) crystallize out of the magma.


Effect of Impacts on the Evolution of Planets

Impacts are very import to the evolution of planets. Planets formed as a result of impacts (accretion) and after that their surfaces continued to be modified by impacts (e.g., Meteor Crater). Impacts may have also controlled how long the Lunar Magma Ocean took to cool.

As the Lunar Magma Ocean cooled over time, it would have formed a floatation crust. That floatation crust would have primarily been made of a rock type called anorthosite. The reason why anorthosite floated in the Lunar Magma Ocean was that it was less dense than the surrounding magma. As the floatation crust grew thicker, it would have acted as a blanket and would have slowed the cooling of the Moon. Now imagine if you had a number of impacts that occurred at that point. Some of those impacts may have been energetic enough to break through the floatation crust. That is important since a punctured crust would have been able to lose more energy and in turn speed up the cooling of the Lunar Magma Ocean.

This part of my research involves using a computer program called iSALE that has been developed over the years by a number of researchers to model impacts.

Image by truthseeker08 on Pixabay

Lack of Diversity in the Geosciences

The geosciences as a collection of fields (e.g., planetary science, geology, atmospheric science, etc.) is not demographically diverse. As an example, a recent study found that over the past 40 years there has been no improvement in the racial and ethnic diversity of those who obtained Ph.D. degrees (Bernard & Cooperdock, 2018). While this is one measure, there are many others that show the same basic idea. The geosciences needs to do better.

A group of us are working on a paper that proposes educators need to deliberately consider students’ emotions to help them when they face social blights such as racism, sexism, homophobia, xenophobia, and ableism during their education. If you would like to read the preprint, please click on the link below.


Past Research

A computer simulation of a rubble-pile asteroid experiencing repeated shaking due to impacts and undergoing size-sorting of constituent particles (i.e. the Brazil Nut Effect).

Brazil Nut Effect on Asteroids

Asteroids are likely a collection of smaller particles largely held together by gravity. These rubble-pile asteroids can be size-sorted as impacts shake them. The shaking by impacts can lead to the Brazil Nut Effect, which is when larger particles in a loosely held collection of particles rise as smaller particles fall. This may be seen on asteroids such as Itokawa (see how the larger particles seem to be on the surface?)

The animation was generated by running a discrete element modeling computer code called pkdgrav. As this modeled asteroid is shaken, the smaller (yellow) particles fall into the center while the larger (red) particles rise to the surface.

Image by ArtsyBee on Pixabay

Students’ Attitudes Towards Science

As part of my dissertation work, I studied how students' attitudes towards science may affect their course performance. I did statistical analyses on surveys taken by students of 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.

Students were given the survey at both the beginning of the course and at the end. Students were asked to choose responses based on a Likert scale. For example, they were asked to rate how much they agreed or disagreed with items such as "Creativity does not play a role in science" and "I can do well in science courses.” One of the interesting findings of this work is that students enrolled in fully-online degree programs have better attitudes towards science than their traditional in-person degree counterparts.

Image by igorovsyannykov on Pixabay

Informal Education with AM Radios

Informal education is generally learning that takes place outside of “formal” education environments such as schools and universities. It is often driven by an individual’s own interests. If you happened to be curious about radios and started watching YouTube videos about them, that would be an example of informal education.

Informal education is very important since people generally only spend a small fraction of their lives in formal education settings. Thus, to help people to learn continuously not only do we need to make informal education more widely available but we also need to study its effectiveness to make improvements.

To help with that effort, we interviewed folks who came to open house events at the School of Earth and Space Exploration (Arizona State University). Specifically, we interviewed those who participated in a Build Your Own AM Radio activity. We conducted 41 interviews and found several interesting patterns. At least half of all participants were parents and it was clear that the main reason why they came to the open house was to expose their children to science. Another finding was that even those with a lot of experience in electronics seemed to learn something from the activity. For example, one individual stated, "The design of the transmitter and the receiver itself is completely complicated based on me studying for 10 years trying to understand what a transmitter and receiver is. But just in five minutes I found that I could really built [sic] it by myself." Yet, we find that certain individuals maybe missing out. Parents with little, some, or a lot of experience with electronics experience seemed to bring their children to the open houses. Yet, those who did not mention that they had children were mostly individuals with some electronics background. We can speculate that they came due to their interests or curiosity. So individuals who have little or a lot of experience with electronics may be overlooking this informal education opportunity. Thus, to improve public understanding of science, informal learning centers should continue to consider ways to make events more accessible and more enticing for people who may not be experiencing valuable learning opportunities such as this activity.

Topography data from the Lunar Reconnaissance Orbiter (LRO). Figure by Mark A. Wieczorek.

Topography data from the Lunar Reconnaissance Orbiter (LRO). Figure by Mark A. Wieczorek.

The Shape of the Moon

As part of my master's degree, I worked on the lunar asymmetry problem. Due to the fact that the Moon is tidally locked we can only see the nearside of the Moon (left side of the image) from the Earth while the farside of the Moon (right side of the image) faces away from us. It has been long known that the nearside and the farside of the Moon are geologically distinct. For example, the darker areas that you see when you look at the Moon at night are the result of ancient volcanism and are concentrated on the nearside. In addition, certain interesting chemical elements, such as thorium, are also 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.

Our work involved analyzing topography and gravity data to understand what processes would have established the large-scale features of the Moon. Our work shows that the large-scale topography and gravity of the Moon are due to two reasons: (1). The Moon freezing into a certain shape at a time when the Moon was hotter and closer to the Earth (2). The crust of the Moon being tidally heated, thus making regions near the equator thicker while the regions near the poles thinner.