Jens Barosch studies stardust to understand our Solar System

Almost all elements in the periodic table are produced in stars.

Some condensed to form solid mineral grains—literal stardust. These stardust grains were part of the molecular cloud from which the Solar System formed. They were here before our Sun, thus “presolar.”

Most presolar dust was vaporized when the molecular cloud collapsed—forming the Sun and an orbiting disk of debris that would ultimately turn into the Solar System as we know it. Any surviving presolar dust grains were trapped in asteroids, where they remained for billions of years. They are smaller than bacteria, extremely rare, and can only be identified with sophisticated microanalytical techniques like those we have at the Earth and Planets Laboratory.

Postdoctoral Fellow Jens Barosch recently discovered these rare presolar grains in a sample of the asteroid Ryugu, which was returned to Earth via JAXA’s Hayabusa II mission. These grains help us understand the chemical makeup of our cosmic neighborhood before our Solar System was formed. They also help us understand what type of stars birthed the elements that makeup Ryugu, our planet, and even ourselves!

His work on the Ryugu asteroid was recently published in The Astrophysical Journal Letters. 

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To start, can you introduce yourself?

Hi, I’m Jens from Heidelberg, Germany. I am a postdoctoral researcher at the Carnegie Institution, Earth and Planets Laboratory. I study rocks from space in the laboratory that came to us as meteorites or were returned by space missions.

The petrology and composition of these rocks and of their components tell us how the Solar System formed from a cloud of dust and gas. 

What would you say is the coolest thing about your work? 

The coolest thing about my work is slurping my morning coffee while checking how many stardust grains I found in last night’s measurement. This can backfire. If there are none, my disappointment is immeasurable, and my day is ruined. 

What is the most challenging part of your work?

My work is highly interdisciplinary and I often need to understand what my colleagues from different backgrounds are doing. This includes, for example, understanding astrophysical models of galactic evolution, considering new astronomical observations, or learning about complex reactions involving organic compounds. This can be very challenging to understand but it is necessary to place my own findings into a larger context.

Another major challenge is navigating academia. It’s hyper-competitive, positions are short-term and funding is very limited. I always have to be on the lookout for new opportunities instead of focusing on my research. Even if I found my happy place in DC, I might end up somewhere completely different. The lack of long-term perspectives is a systemic problem in academia that needs to be addressed if we want science to progress. 

What are the larger implications of your research?

There are several big questions that we have been trying to answer since the dawn of humanity, for example, “where do we come from?”, and “are we alone?”. In the age of space exploration and modern analytics, we might be closer to an answer than ever before. I would be extremely happy if I could contribute a tiny piece of the puzzle through my research. 

What inspired you to choose this field of study? 

I have always been fascinated by the natural world, including geological sights and the night sky. I grew up in a small village with relatively dark nights and used my dad’s telescope to look at the stars and planets. This certainly inspired me and influenced my decision making when choosing courses at university. In the end, however, I still think it is a huge coincidence that I ended up exploring the cosmos professionally.

Recently, you’ve been studying samples from the asteroid Ryugu. What have you found so far?

The Hayabusa2 mission recently returned samples from asteroid Ryugu. Pieces of the asteroid were distributed to several international science teams for the initial analysis phase. Several Carnegie scientists are involved in this project.  

At Carnegie, we’re focusing on analyzing organic matter and presolar grains in the Ryugu samples. Our first publication has just been released online in The Astrophysical Journal Letters. 

The Ryugu samples are among the most primordial rocks we have access to. They can tell us what the early Solar System looked like. They resemble a rare group of meteorites found on Earth, but the Ryugu samples were not modified by any Earth-bound processing. Even still, the geologic processes on the asteroid (described below) destroyed many of its primary constituents. 

Our team detected presolar grains—extremely tiny and rare grains of dust that are older than the Solar System. 

They are made from silicon carbide and are relatively resilient to destruction. We expected to find them in Ryugu because they are also present in some meteorites. However, we also detected other types of presolar grains that we did not expect—they are very delicate and should not have survived on the asteroid. They must have been shielded from destruction.  

What sort of information can we get from presolar grains?

Presolar grains carry unique isotopic fingerprints that reflect the type of star which produced them. By analyzing their compositions, we can learn how stars synthesized elements and their isotopes (i.e., versions of the same element with a different mass).

Studying presolar grains is the only known way to directly examine some of the building blocks of the Solar System in the laboratory. These tiny grains can tell us what type of material and which processes ultimately formed the Sun and planets. 

What sort of processes can destroy presolar grains?

Extraterrestrial samples are called “pristine” if they were not modified by any secondary processes after their formation.

Typical secondary processes that occur on asteroids are heating (thermal metamorphism) or alteration by fluids like water. These processes modify or even destroy the primary constituents of asteroids, particularly delicate presolar grains. 

Most meteorites were further affected by weathering on Earth, while the Ryugu samples were not. Still, the Ryugu samples are not considered pristine because they have been significantly altered by circulating fluids on the asteroid. Only very resilient types of presolar grains such as silicon carbides may survive this alteration process. 

How did it feel when you first saw the Ryugu samples? 

They look rather unspectacular until you think about their remarkable journey.

Asteroid Ryugu has been floating through space for billions of years until humans decided to build a spacecraft and programmed it to scoop up some dust from its surface and bring it back to Earth. I felt that being entrusted with some of this precious and unique material was a great privilege.  

What's next for this project? What are you looking forward to? 

We were surprised to find very delicate presolar dust in Ryugu.

It is limited to tiny areas that were somehow shielded from destruction. We would like to identify more of these delicate grains and understand how they survived on the asteroid. We just received a new batch of Ryugu samples that might be less altered than the previous samples. There might be a chance to find more delicate dust when we look at them in detail in the coming weeks.  

Do you remember the first time you thought you'd be a scientist? 

No, and it still feels unreal at times.

What has influenced your thinking as a scientist?

Probably more than anyone, my advisors Dominik Hezel (during my Ph.D.) and Larry Nittler (at Carnegie and now Arizona State University). Both are brilliant scientists and great mentors. Working closely with them has significantly shaped how I approach my work.

I also learn a lot from connecting with other Carnegie postdocs. It is a diverse group from different backgrounds, with different ideas, experiences and research strategies. Talking to them definitely influences how I approach my own projects. 

What do you like to spend your time on when you're not researching? 

That rarely happens! When my brain batteries need recharging, you’ll find me running in the woods. Sometimes, that’s where I have the best ideas.

Why did you choose Carnegie's Earth and Planets Laboratory? 

The Carnegie Institution is a great place to be a researcher. They provide me with everything I could ask for to conduct my research successfully: A great work environment, cool colleagues, and state-of-the-art equipment. I applied, and was lucky to be chosen and I am very grateful for the opportunity to work here.

Do you have any advice for current grad students? 

You need two things to be successful in science: A project that you’re passionate about and a good supervisor to support you. Both are incredibly important, and if either doesn’t fit, you’re in for a rough ride. Don’t hesitate to get help when you notice that things are not working out.

Anything else you'd like to add? 

I am always happy to talk to people interested in my research or students seeking advice. Please feel free to contact me!