Why This NASA Satellite Is Studying Plankton

12:16 minutes

Did you know you can see plankton … from space? Earlier this year, NASA launched a satellite to do exactly that. It’s called PACE, which stands for Plankton, Aerosol, Cloud, and ocean Ecosystem, and NASA hopes that the satellite can tell us more about how these tiny creatures interact with Earth’s atmosphere and influence our climate.

Some species of plankton, called phytoplankton, are microscopic plants that absorb carbon dioxide and produce oxygen. PACE has equipment that can identify different species of phytoplankton by the kind of light they give off, giving NASA real-time information about their location and population size, which can also aid fisheries and coastal communities when algal blooms occur.

An aerial view of the ocean, with pools of bright green spreading over its surface.
During the spring and summer in the Barents Sea, north of Norway and Russia, blue and green blooms of phytoplankton are often visible. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite captured this true-color image in 2021. Credit: NASA Earth Observatory

PACE will also study how aerosols affect air quality on Earth. Additional instruments on the satellite can differentiate between different kinds of aerosols by studying how they reflect light back into space, which will help scientists refine their climate models so that more accurate forecasts can be made.

Ira Flatow talks to Dr. Ivona Cetinic, PACE’s science lead for ocean biogeochemistry, about the satellite, her favorite species of plankton, and how the public can benefit from the data that the mission will provide.

Further Reading

Segment Guests

Ivona Cetinic

Dr. Ivona Cetinic is a senior research scientist at NASA and the Science Lead for Ocean Biogeochemistry for PACE. She’s based in Greenbelt, Maryland.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Later in the hour, we’ll get a behind-the-scenes look at the ambitious NASA mission that retrieved a sample from an asteroid. And we’ll remember famed primatologist Frans de Waal, who passed away last week.

But first, did you know that you can see plankton from space? Yeah, earlier this year, NASA launched a satellite to do exactly that. It’s called PACE, which stands for Plankton Aerosol Cloud and ocean Ecosystem. And NASA hopes that the satellite can tell us more about how these tiny creatures interact with Earth. And can we use them to mitigate climate change?

Here to fill in the details is Dr. Ivona Cetinic, Science Lead for Ocean Biogeochemistry for PACE, based in famed Greenbelt, Maryland. Welcome to Science Friday.

IVONA CETINIC: Thank you. So happy to be here.

IRA FLATOW: Nice to have you. I understand you just got this satellite up and running, right?

IVONA CETINIC: Yes, we launched PACE, like, 40 days ago or something like that. And it’s running, and it’s doing everything what we want it to do and even more, so we’re really excited.

IRA FLATOW: Wow, I want to hear more about that, but I think we need to get into some of the details about just why you study plankton. Tell us what plankton does. Why is plankton so important to our planet?

IVONA CETINIC: For sure. So plankton are microscopic creatures that live in every aquatic system and ocean as well. And you can kind of separate them into zooplankton, which are kind of like teeny-tiny animals. And then you have the phytoplankton, which are teeny-tiny plant-like creatures.

And while invisible to our eyes, they’re very, very important because they, in a sense, do three things for us, like three services. First one is they kind of draw carbon dioxide from the atmosphere and make it into the sugars that feed most of the food web in the ocean, so everything that we like, dolphins and things like that.

And third thing is the fact that they produce oxygen. So around 50% of the Earth’s complete oxygen is produced by phytoplankton. So that’s really important for something that is so teeny and invisible.

IRA FLATOW: Wow. And what would our planet look like if we didn’t have plankton if it’s that important? It would look a lot different.

IVONA CETINIC: Yes, very, very different. I mean, the first oxygen came from the creatures that we call plankton today. So without that first oxygen, nothing else would evolve. But if I would take away plankton now, oceans would die, climate would change. We would not have anything to eat. So it would be very, very sad place, and probably we wouldn’t care because we would be dead.

IRA FLATOW: [LAUGHS] Yeah. And another really interesting thing about them is that there’s just an enormous diversity of them in our oceans, right?

IVONA CETINIC: Yes, that’s true. And that’s a diversity that we can just usually observe by going out on the ships and taking samples and looking under the microscope. But ocean is gigantic, and we can’t be everywhere with ships. So that’s why we built PACE, so we can see this diversity of the plankton from space.

IRA FLATOW: Mmm, all right, so tell us what– now we’re at the point where you can tell us. What does this satellite do? What kind of mission is it on?

IVONA CETINIC: So PACE is the satellite itself. And it carries three different instruments, and which are the ones that are going to give us this view of the Earth in an unprecedented way. One is called OCI, which is Ocean Color Instrument, which is a hyperspectral instrument, so meaning that– think about you walk through your life carrying a cell phone that’s kind of like a Nokia, like the old-school Nokia, the flip phone, where you take a photo and looks ugly.


IVONA CETINIC: That’s what we had for last 20 years. And that showed us that ocean is full of phytoplankton, but we didn’t have any idea what type of phytoplankton it is. So PACE will allow us to see that, which allows us differentiation of different types of phytoplankton so we can understand how they’re changing or helping us or changing the climate, helping our ecosystem, helping our tourism, and so on.

There’s two teeny-tiny instruments that are also attached to PACE, and they’re polarimeters. So they’re looking at the color of the ocean, but they’re also looking at ocean and atmosphere from different angles, but also looking at the polarization of the light, which is kind of weird to explain. But think about your sunglasses, you know, when you’re have them during the summer, and you tilt your head, and everything kind of looks different.


IVONA CETINIC: That’s what they’re measuring. They’re measuring that polarization. That information can tell us a lot about clouds and aerosols, which are crucial for climate but also our own health.

IRA FLATOW: Yeah, and that’s the other thing. PACE is not just going to be studying the plankton. It’s going to be gathering data on the aerosols’ effect on the planet. Tell us why the aerosols are so important.

IVONA CETINIC: So both aerosols and clouds. So aerosols are crucial just from the perspective of each of us individually because those are the things that are changing the quality of the air. When the air quality goes down because the smoke comes from the Canadian fires, that’s aerosols. Aerosols can also be dust particles. There’s many different types of aerosols. Understanding the diversity of the aerosols is as important as understanding the diversity of the phytoplankton.

What is crucial, really, that PACE is going to be able to see because it’s going to look at both clouds and aerosols is these teeny-tiny interactions that happen between these two different components of the atmosphere. That’s the biggest source of uncertainties in a climate model. So understanding how aerosols form clouds and how clouds interact with the aerosols and the way that PACE is going to be seeing it is going to allow us to understand better that interaction, put it in our models, be able to predict the impacts of the climate in future in a better way.

IRA FLATOW: And the irony of some aerosols is that they actually may help mitigate the greenhouse gas effect, right?

IVONA CETINIC: Exactly. I mean, aerosols bounce the light. So there’s so much unknown about the aerosols. And having this continuous hyperspectral polarizing view of the Earth is going to be crucial to bring a majority of these questions that we have about what aerosols are doing, what clouds are doing, and then give us these answers that we really need.

IRA FLATOW: I know you were talking about the species of plankton that sequesters carbon and produces oxygen. They kind of sound like the trees of the seas. There have been ideas I remember over the years being put forward about feeding the plankton in the ocean so they could soak up more of the CO2. And if I recall, it was an idea of spreading iron–


IRA FLATOW: –in the ocean to stimulate growth. What’s happened with that?

IVONA CETINIC: So I think the original idea of dumping iron in the ocean to support phytoplankton growth started long time, like, 20, 30 years ago in oceanographic circles. And it is true that certain parts of the ocean are limited by the iron. So if you dump iron, the phytoplankton is going to start growing and responding. And you can actually see that from space. We do have images.

Now, currently, as we’re looking to the– as we as a community are looking for the solutions for the changing climate, there’s lots of ideas that are being boiled under this idea of marine carbon dioxide removal, where those experiments would be repeated. And PACE will definitely be supporting the exploration of these things.

So we are kind of in a stage that we don’t understand completely the oceanic– the way that ocean works, the way the ocean ecosystems work. So I think in future years, there’s going to be lots of funding going towards understanding better the response of the ocean to those iron supplements in order to actually go further down the line in future and actually doing that or not. We really don’t understand it, and that’s why us observing the impact of those experiments are important. And that’s where PACE can come in, definitely, to see what’s going to happen.

IRA FLATOW: Because you don’t want unintended consequences.



IVONA CETINIC: Exactly. It’s like, we have so many examples from the history of humankind where we play with the nature, and nature responds in a very specific way. And if you don’t understand the ecosystem well, you really cannot tinker with it. So different types of phytoplankton will success– will be really, really good in exporting carbon. Some other type of phytoplankton will be really bad in exporting carbon.

And dumping iron and not understanding what kind of phytoplankton is going to grow would be kind of silly. So there’s lots of, I think, currently, investments happening to understand the ecosystem response better before actually moving onward with true climate corrections and things like that.

IRA FLATOW: Yeah. That’s always a good idea.


IRA FLATOW: To get some data.

IVONA CETINIC: Let’s start small, and then maybe, you know.


IRA FLATOW: Well, let’s talk about what are some of the measurable things, the public outcomes, that could come from PACE.

IVONA CETINIC: So as you said it yourself– I mean, plankton is dear and near to my heart, so let’s start there. So we were able to see green from space. And by seeing green, you don’t know anything. There’s certain type of phytoplankton, as I said, that are really good in exporting carbon. Some of them are bad. And just understanding that difference, the fact that we can see that from space, is really important because now we can put that in our climate models.

On the other side, if you like going to the beach, and there’s a harmful algal bloom brewing, if you’re a person that has to close the beach, or it has oysters, or it has anything that that’s dependent on that water, that coastal ocean, you really want to know what’s brewing. And PACE is going to be able to see that water quality. Great Lakes, fisheries– fish will eat specific things in the ocean. And understanding what is the abundance of those specific things is very important for, for example, NOAA to be able to predict the fisheries’ yields in years to come.

So those are the results on the side of ocean. But similar things come from the atmosphere. Once again, diversity of the aerosols, where are they coming, how are they forming, how they’re interacting with clouds– super crucial not only for climate, but also for understanding of the air quality and human health.

IRA FLATOW: NASA, I understand, put out a video that you’re featured in–


IRA FLATOW: –explaining the PACE mission. And they also made a ’90s-themed toy commercial explaining different species of plankton. And we have a little clip from that. And let’s hear that.

SPEAKER 1: (SINGING) Phyto Phyters! Microscopic warriors fighting for the sea.

SPEAKER 2: These tiny titans, the Phyto Phyters, are out to do battle on the seas. But Protoperidinium lights up the battle with its bioluminescence.

SPEAKER 3: Go, Emiliania!

SPEAKER 2: Only the Phyto Phyters will decide the true fate of the seas. Each sold separately.

IRA FLATOW: Oh, that is cute. That is cute.

IVONA CETINIC: We have amazing producers. I’m just going to say that. That’s Ryan and his amazing brain.

IRA FLATOW: Do you have a favorite species of plankton? I know you love plankton so much.

IVONA CETINIC: Yes, I do. It’s not really a popular species, but it’s a really pretty, pretty type of phytoplankton. It’s a silicoflagellate. That means it has a shell, like the bone’s made out of the glass. And it has a beautiful shape that really reminds me of the star on PACE’s logo. That’s my favorite type of phytoplankton.

IRA FLATOW: OK, so you’ve got this satellite up. You’ve got lots of great hardware on it. Now, if I could give you a blank check on what you would really like, what would you spend it on? What do you need to know? What would you like to know about the aerosols and the plankton that you don’t? And what kind of hardware, or how would you spend that money?

IVONA CETINIC: Oh, so like, I can build a new mission?

IRA FLATOW: Yeah, yeah.


IRA FLATOW: Tell me what you’d like.

IVONA CETINIC: Oh, wow. So yeah. [LAUGHS] Well, now, when you give me all this money, for sure.


IVONA CETINIC: There’s something called lidar, which is a type of laser. And what that lidar allows us is to see deeper in the ocean. One thing they didn’t say about PACE is we see only the surface of the ocean. And that’s where, to an extent, plankton is sitting on it. It likes sunlight. It’s sitting really close to the surface of the ocean. But we don’t see past that surface.

Lidar can see deep into the ocean– I mean, not super deep, but deeper. So I’m really interested the role that phytoplankton plays in the flow of carbon. But I’m also interested, Where does that carbon go? Which pathway does it take in the ocean? And with lidar, I’ll be able to see that. So I will take your check.


IVONA CETINIC: I’m going to make a mission that’s going to have a lidar with a couple of different colors. And I’m going to fly it globally. And that’s going to give me the answer to the next step of my science exploration. Thank you. [LAUGHS]

IRA FLATOW: Well, the check is in the mail, but I wouldn’t wait too long for it.


IRA FLATOW: Thank you for telling us about your mission and your dreams, Dr. Cetinic.

IVONA CETINIC: You’re welcome. Thank you for showing enthusiasm about something that I really, really love, which is PACE mission, the coolest mission ever.

IRA FLATOW: Dr. Ivona Cetinic is Senior Research Scientist at NASA.

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