IIf you’re trying to spot phytoplankton, it pays to get really close. Among the smallest forms of life that inhabit both fresh and marine waters, phytoplankton can measure just a micrometer – or a millionth of a meter. But little things can have a big impact. Blooms of phytoplankton, which is actually a form of microalgae, can spread over hundreds of square kilometers, sometimes causing disastrous damage to fisheries, beaches, drinking water supplies and entire aquatic ecosystems. To track such an extensive scourge, you need to stay at a distance equivalent to 675 km (420 miles). That’s the altitude at which NASA’s new PACE satellite — short for Plankton, Aerosol, Cloud and Ocean Ecosystem — will orbit, following its planned February 6 launch.
Formally authorized in 2015, PACE will continue the more than two-generation work that NASA began in 1978 when it launched the Nimbus-7 satellite, the first spacecraft built to observe phytoplankton in the ocean and study its broader role in influence of the environment. But befitting a modern era in which we know much more about environmental science as a whole and climate change in particular, PACE is a smarter, more agile ship that will take the pulse of the planet in two important ways.
The first will directly address the issue of phytoplankton, and for government, industry and environmental scientists this is important for a number of reasons. Large living mats can sometimes be beneficial – absorbing carbon from the atmosphere and fixing it at the base of the food chain, where other larger organisms can intervene. But the toxins produced by algae can also kill fish and other aquatic life, and in humans they can cause diarrhea, paralysis, dizziness and memory loss, as well as abnormal liver function, vomiting and numbness.
“We need eyes in the sky on this because [phytoplankton] they grow very quickly, on a scale of hours to days,” says Jeremy Werdell, project scientist for the PACE mission. “They’re also in a rotating, three-dimensional fluid, so if you don’t see them today, they’re likely to be there tomorrow.”
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Phytoplankton scanning isn’t all PACE will do. A second interrelated environmental factor that can affect climate change is atmospheric aerosols – floating clouds of smoke from wildfires, desert dust, volcanic ash, urban industrial smog and even sea salt that has evaporated with ocean water and was taken to heaven. Aerosols create a kind of floating shadow, which, depending on their color, composition and particle size, can absorb incoming solar energy – thus exacerbating global warming – or reflect it back into space, thus lowering the thermometer.
“I wouldn’t use the term greenhouse effect,” says Werdell. “This is normally reserved for gases, not particles. But the principle is the same in the sense that some radiation balance is involved.”
PACE, which will blast off aboard a SpaceX Falcon 9 rocket, scheduled to launch February 6 at 1:33 a.m. EST, is a relatively small machine as satellites go — weighing 1,700 kg (3,750 lbs) and measuring 1.5 m (4.9 ft) high. NASA could keep PACE compact because the satellite carries only two pieces of science hardware: an ocean color instrument (OCI) and a multi-angle polarimeter.
As its name suggests, the OCI was designed to measure the color of ocean water, making fine distinctions between various wavelengths of the spectrum to determine the chemical composition of different regions and, in turn, the types of organisms that call these regions. home areas. , particularly various types of phytoplankton. Different species of algae come in different shades, typically green or blue, but also, more dangerously, red. The latter is capable of producing so-called red tides, which release highly persistent toxins that move up the food chain as smaller fish consume them, larger fish eat smaller fish, and so on. This, of course, assumes that the smaller fish survive and, depending on the concentration of toxins they consume, this often does not happen. A red tide in Florida in 2021 left 600 tons of dead fish on the beaches of Tampa Bay.
“PACE measures the entire color spectrum,” says Werdell, “from ultraviolet to near-infrared. This is new information that allows us to not only say that we see phytoplankton, but what community of phytoplankton they constitute.”
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Distinguishing organisms is important because phytoplankton not only have varying levels of toxicity, but also varying metabolisms and sizes. Collecting this data will help scientists understand how emissions are trapped or released by the oceans. Some phytoplankton absorb more carbon than others – absorbing it from the atmosphere and reducing its ability to cause global warming; some are larger – and therefore sink faster and further – sequestering the carbon they collect deep in the water column. Phytoplankton also release gases into the air, giving atmospheric water microdroplets something around which to nucleate and eventually leading to cloud formation. These, in turn, reflect sunlight that heats the planet. “Organisms are really important pieces of the puzzle,” says Werdell. The long-term goal is to learn more about the cycle of gas and cloud exchange between the ocean and the atmosphere and better understand how this changes our climate.
The polarimeter studies the other piece, looking at aerosols in the atmosphere – mainly by measuring the oscillation of sunlight as it passes through the air. This is an essential – and currently incomplete – area of research. Like most scientific graphs, those published by the United Nations Intergovernmental Panel on Climate Change (IPCC) include so-called error bars to indicate the degree of uncertainty in any data set. “The IPCC has numbers that detail different contributions of things that can warm and cool the atmosphere,” says Werdell, “and right now, the biggest error bars are in the anthropogenic aerosol distributions.”
He and the rest of the PACE team aim to fix that, collecting data that will help environmental scientists study aerosols and gather clues to determine the pace and severity of future climate change. “By making these measurements,” says Werdell, “we can understand how different components of the atmosphere are interacting – with some things warming and others cooling. It’s very, very important to know all of this.”