Credit: NASA/Scott Battaion
NASA's GUSTO mission – short for Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory – has an out of this world mission: to measure emissions from the interstellar medium, which is the cosmic material found between stars. GUSTO took flight on a zero-pressure balloon carrying a telescope with carbon, oxygen and nitrogen emission line detectors from McMurdo, Antarctica in late 2023. The data collected will help scientists determine the life cycle of interstellar gas in our Milky Way galaxy. Christchurch-based scientist Christopher Martin discusses the project, and the importance of Christchurch as a gateway to Antarctica.
Why did GUSTO launch from Antarctica?
Firstly, we're observing around a part of the sky called the Galactic Centre in the constellation of Sagittarius. Because it’s in the southern part of the sky, it makes a lot of sense to launch from a southern hemisphere location.
The second reason is geopolitics. A balloon is like a really high-flying airplane. So, you have to worry about airspace and what countries you're crossing over. The Antarctic Treaty gives you a lot more leeway for doing science projects like that.
What’s your involvement with the GUSTO mission?
Based in Christchurch, my day-to-day activity is science data reduction. After a successful launch like this, you need to turn the data around into a format that the broad worldwide science community can use.
Why is it important that we know about the life cycle of interstellar gas in the Milky Way?
There's a common saying – we’re all made of star stuff. When the universe was first created, it was just hydrogen and helium and a tiny trace amount of lithium, yet we see ourselves as carbon, nitrogen and oxygen, all these atoms that are absolutely crucial to life. Where did they come from?
As the early stars in the universe grew, they did their cooking of hydrogen into higher elements like carbon, nitrogen and oxygen. When they blew up they sent their material out into interstellar medium (ISM). As new stars – such as our sun – formed, they grab that material that's been enriched in these elements. So the sun is using material that came out of the ISM that was cooked through at least two previous generations of stars. Tracking this whole life cycle helps us learn how elements like carbon and nitrogen ended up on Earth and in the Solar System writ large.
What makes GUSTO particularly exciting and innovative?
GUSTO can fly up to 35 kilometres above the atmosphere, making these lines of carbon and nitrogen much easier to see. Previously we’ve only been able to look at very small, targeted areas. What GUSTO can do is make a map of a huge chunk of the skies. It’s far and away the largest and most detailed map of these lines that has ever been made.
Were there any particular challenges with this mission?
Balloon missions by design are purposely riskier than satellite missions, because you're using more cutting-edge technology. You're constantly having to figure out how to make these things work. The space environment is even more challenging than Antarctica itself. Antarctica is cold, but at least it's got sea level pressure. As the balloon starts to go up, it's above 99% of all the Earth's atmosphere, so you're almost in a pure vacuum.
The side of the balloon that's facing towards the sun gets hot, the side that's facing towards the shadow gets cold. You've got to figure out how to balance heat in an instrument that's essentially in vacuum.
What kind of insights have you gathered so far that you can share?
We've got images of some well-known clouds, both in our galaxy but also in our neighbouring galaxy, the Large Magellanic Cloud. And so we're seeing all of these lines in those places. The real test is when the astronomical community sees it and how excited they’ll be to test out theories that they've been cooking up for many years.
Why is Christchurch such an important gateway to Antarctica?
Antarctica is a very inhospitable and difficult continent to get to. You need access points that let you get to the various parts and in particular, the Ross Sea region. Christchurch is very well suited for that, by air and by sea. Thousands of people transit through Christchurch every year on their way to and from the Antarctic continent.
And that connection is certainly appreciated. NASA felt that GUSTO was so important that they dedicated their one and only C-130 aircraft to carry the telescope all the way from the US down to Antarctica – via Christchurch.
How has being based in Christchurch been beneficial for you, as a scientist?
Some of the key people I collaborate with are at the University of Canterbury. Other projects that have happened in Antarctica have strong UC research connections, including the IceCube Neutrino Observatory in Antarctica, which in 2023 produced a neutrino image of the Milky Way using a huge telescope buried in the ice at the South Pole.
What does NASA’s GUSTO programme tell us about the intersection of science and Antarctica?
The great thing about the GUSTO mission is that it highlights the incredible science happening in Antarctica – and Christchurch is playing a pivotal role in that. Without the tremendous support provided by the city, the work done by NASA and the U.S. National Science Foundation wouldn’t be possible. It takes a big team to make a mission like this a success, and Christchurch is certainly part of that team!
