Audrey Martin, Planetary Geoscientist

I am a planetary geoscientist, which means I study rocks from other planets and asteroids in the solar system! More specifically, I study a group of asteroids called Trojans. Most asteroids in the inner solar system are found in the Main Asteroid Belt, however Trojans are found further out. They orbit in two swarms and share an orbit with Jupiter (Figure 1). They have gravitationally stable orbits around the Sun, and probably haven’t moved for nearly 4.5 billion years (almost the age of the solar system!). Asteroids like this are called ‘primitive bodies’ and hold useful information about the environment in the early solar system before planets were made. I use Trojan asteroids to reconstruct major events that shaped our solar system.

Everything we see comes from photons in a very small sliver of the electromagnetic spectrum called the ‘visible.’ Trojan asteroids are some of the darkest objects in the night sky, so I ‘look’ at them in the thermal infrared (TIR). All objects in the universe radiate heat in the form of photons, and I look at the heat radiated by Trojans. This is basically how night vision goggles work! Using TIR data, I can examine the surface characteristics of Trojans (i.e., what minerals are present and texture) that are useful in determining their formation environment. By knowing how and where Trojans formed we learn more about what the solar system was like billions of years ago.

This is a figure of the relative positions of the inner planets (Mercury, Venus, Earth, and Mars) as well as Jupiter. The main belt orbits the sun between Mars and Jupiter. Notice the Trojan asteroid swarms, in orbit with Jupiter. This figure is definitely not to scale! From Planets for Kids, click through the image to get to their website!

Trojan asteroids are useful as ‘planetary fossils’ because they have been relatively undisturbed since the early days of the solar system. As such, they hold clues that are crucial for our understanding of the evolution of the solar system and planets. In 2021, NASA will launch Lucy a mission to the Trojan asteroids. The mission was aptly named after the fossilized hominid skeleton which helped form much of our knowledge on human evolution. In a similar manner, Lucy will collect data that are integral for understanding planetary formation and conditions in the early solar system.

My favorite part about being a scientist is learning more about how our solar system formed and gaining perspective on how precious Earth is. It is tremendously humbling to be a planetary scientist and research rocks that were formed in the solar nebula billions and billions of years ago, using data from spacecrafts that are currently over 200,000,000 km from Earth. And with the same spacecraft we can look back to Earth and see a small rocky planet, host to all the life we have ever known.

My advice to young scientists is to remain curious and keep asking questions. What you will find is with every question answered two more pop up, but keep asking. Sure, life as a scientist can be difficult, but that is not unique to a career in science. The unique aspect of being a scientist is that we get to expand the ‘bubble’ of human knowledge. As scientists, our endeavors are only limited by complacency. We will never know all that is there to know, but it is our job to keep searching and learning and discovering by asking questions.

Animations of Trojan Asteroids as they co-orbit the sun with Jupiter

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