At the bottom of the stairwell leading to deck five, an alien lies upturned on green nonslip flooring. If you get close enough, you can see one of its six legs twitching and one of its translucent wings crushed to pieces. Unlike the throng of Antarctic expeditioners aboard the RSV Nuyina, Australia's newest icebreaking ship, it hasn't cleared customs.
Days after the Nuyina departed its harbor in Hobart, Tasmania, the alien buzzed its way across the Derwent River, slipped through an open door and zipped into the bowels of the ship until this restless, twitching death.
Scientists call the creature Musca domestica. You likely know it as the housefly.
Even if it hadn't been felled by an errant hand or boot, it likely wouldn't have survived the journey to Antarctica. At temperatures below 14 degrees Fahrenheit, flies move lackadaisically and seem to barely get airborne. I know this because I've been watching them as part of the crew onboard the Nuyina as it crosses the Southern Ocean. Surviving flies buzz at the ship's windows, trying to escape the upper decks.
If their prison break were to succeed, they'd find themselves facing seemingly endless waters, with nowhere to go. The Southern Ocean provides a formidable barrier to entering Antarctica, a great wall of water and powerful currents that has separated the continent from the rest of the world for about 30 million years. Couple that with freezing temperatures, and the Antarctic provides little hope for a wayward housefly trapped on a ship.
But Antarctica's temperature is changing, and dramatically. In March, a French-Italian base in East Antarctica recorded temperatures 70 degrees higher than average for that time of year. That may just be an unprecedented anomaly, but it's expected the continent's average temperatures could rise a few degrees by 2050. In particular regions, like the western peninsula, the continent is warming at a rate 10 times faster than the rest of the world. In February 2020, the temperature at Argentina's Esperanza Base research station reached 18.3 degrees Fahrenheit – an all-time high – providing the kind of conditions a wayward housefly might survive in.
Historically, it's been difficult for lost flies to reach the most southern landmass on Earth. As Antarctic explorers aimed to discover and map the continent in the 1800s, humans began providing fleeting opportunities for alien trespass. A handful of nations with a permanent presence across the continent annually resupply research stations that provide permanent outposts for studying the ice and the Antarctic ecosystem.
It's become easier to reach the continent and its surroundings by sea or air, but it remains an exclusive club. "Back-of-the-napkin math, less than a million people in the entire history of human existence have visited Antarctica," says Dana Bergstrom, an ecologist at the Australian Antarctic Division.
But that too is changing. Before the pandemic slowed cruises to a halt, Antarctic tourism was on the rise. In the 2019-20 season, almost 75,000 people visited the continent, according to IAATO, the chief tourist body in the Antarctic. That's a 35% increase over the previous season.
Wherever humans go, so too our pests. Signatories to the Antarctic Treaty and the Madrid Protocol, which include protections for the Antarctic environment, must endeavor to limit their effects on the pristine wilderness, and tourist bodies like IAATO and national Antarctic programs go to great lengths to prevent biological invasions. But their strategies aren't bulletproof.
If an alien were to slip in, it could be disastrous for the delicate Antarctic ecosystems hidden from the world for millennia.
"It's a super special place to understand how the planet works," says Bergstrom. "And so it's really worthwhile putting all our efforts to try to keep nature operating without interfering."
On the eastern edge of Antarctica, a collection of shipping containers and sheds lies in an ice-free oasis. Surrounded by a variety of wildlife, including Adélie penguins massed on nearby islands, the base, called Davis, is Australia's southernmost presence on the continent.
In 2014, its hydroponics facility was the site of an infamous alien invasion.
In May of that year, expeditioners entered the facility, composed of two gray shipping containers, to pick fresh greens for the chef's evening meal. They trudged across the snow-covered Davis grounds and opened the door, as if stepping through a portal. They were greeted by the sight of leafy vegetables arranged neatly, the sound of trickling water and, most obviously, heat.
During the vegetable collection, they inspected the facility's water and noticed a black mat had developed over the surface. "When they looked closer, they realized it wasn't a mat," says Andy Sharman, environmental manager at the Australian Antarctic Division, "it was thousands of tiny invertebrates."
Davis had been invaded by The Thing, a thousand times over. An alien species of arthropod known as Xenylla had snuck into the facility and began multiplying in the warm, wet conditions. The flealike critters, known as collembolans, hadn't been seen in this region of the Antarctic before but had become established in warmer areas. A crack team of scientists deduced that should they get out, they might threaten the local ecosystem.
Almost immediately, the station went into eradication mode. "We had a biohazard response like you might get with a virus or disease," notes Sharman.
The effort was blazingly fast. The response team sprayed alcohol throughout the facility, then bagged and burned everything, including recently harvested vegetables that had already made it to the Davis kitchen. The building was subjected to rigorous freeze-thaw cycling; the heat would trick any leftover eggs into hatching and then the temperatures would drop to minus 11 degrees Celsius, killing the hatchlings.
The response team also took extreme social distancing measures. "We actually lifted the whole building out and parked it on the sea ice and left it there," says Sharman. A few months after the discovery and various eradication measures, the containers were shipped back to Australia.
An investigation into the source of the incursion eventually discovered that the aliens likely got in through plant feed. Subsequent monitoring hasn't found the collembolan in the area since, but other stations have experienced invasions, too, and protecting the continent from such risks is a constant battle.
Exterminating The Things at Davis is one of the Australian Antarctic Division's success stories, but the threat of incursion is constant. Invertebrates are the most widely dispersed non-native species and are known to hide in shoes and bags, while plant seeds can become stuck in Velcro and marine creatures can lurk in ballast tanks on vessels.
Australia's Casey Station, on the eastern fringe of Antarctica, has battled outbreaks of a mushroom fly in its sewage system stretching back over two decades. It's likely that the creature made the journey hidden within fresh produce, and efforts to eradicate it have been ongoing. Similarly, in 2017, expeditioners at a Polish base on the Antarctic Peninsula detected a non-native fly in the sewage system. It was able to slip containment and disperse, even though it's not a particularly adept flier and can't tolerate extreme cold, highlighting the continued threat invaders pose to the continent's delicate ecosystem.
Invertebrates lurking in and around human settlements can be tracked, monitored and, hopefully, eradicated. Bergstrom, the ecologist from the Australian Antarctic Division, notes that Australia's strict biosecurity measures have been highly effective so far.
Even so, there are trillions of invaders, invisible to the naked eye, that can slip right past us using their own specialized mode of transport: you.
One of the world's most formidable aliens, SARS-CoV-2, breached Antarctica in March 2020. The trespasser was likely in the airways of a tourist aboard an Argentinian ship that visited several small islands near the Antarctic Peninsula. It wasn't until December 2020, when 36 members of the Chilean Navy stationed at the Bernardo O'Higgins research outpost tested positive for COVID-19, that the virus truly conquered the last of the world's seven continents.
The coronavirus poses a threat to the some 5,000 researchers stationed across the continent and could disrupt or suspend operations at research stations. The virus thrives in the spaces humans have built on the frozen landscape: humid indoor areas where expeditioners constantly come into close contact with one another. Antarctica may be isolated and extremely cold, but humans have built exceptional breeding grounds for the coronavirus.
"Our research stations aren't designed for pandemics or infectious disease control," says Dane Brookes, an expedition medical officer with the Australian Antarctic Division spending the winter at Macquarie Island. "If a COVID case got into a station, it would spread rapidly."
For that reason, those traveling south face extreme restrictions. Before boarding a vessel or plane down south with Australia's Antarctic Division, all expeditioners must be vaccinated and undergo a 14-day quarantine period. Blue-gowned nurses visit isolated expeditioners on three occasions, scraping up any viral particles lurking in throats and noses. If the coronavirus were to get into an Antarctic station, it could be disastrous.
"A single case would essentially shut down a program, ship or a station," says Brookes.
There's also a risk, albeit a very low one, that the virus could infect or take refuge in Antarctic wildlife. "We know that the host range of SARS-CoV-2 is really broad," notes Michelle Wille, a virologist at the University of Sydney. Research has shown that birds are resistant to infection by SARS-CoV-2, which means penguin colonies are likely in the clear, but computer modeling has shown Antarctic whales and dolphins strongly bind the virus. This makes them susceptible to infection, but "without follow-up experiments it's hard to quantify the risk of transmission," says Wille.
Wille and her colleagues compiled a list of recommendations for people visiting the continent in 2020. They follow many of the COVID restrictions we've come to know over the past two years, such as quarantine, predeparture PCR testing and social distancing (though, in this case, not distancing from other humans, but from Antarctica's wildlife).
Though incursions by SARS-CoV-2 have been rare, the threat is ever present. The omicron variant, which caused a surge in case numbers around the world at the end of 2021, reached a Belgian base in January 2022. Many of the nations with routes to the Antarctic are battling outbreaks, which has significantly impacted research activities and prevented access to the continent as bases have locked down. It's unlikely to be the last time the coronavirus invades and, two years after its emergence, it doesn't seem we're prepared for the next incursion.
As the world warms and conditions become more favorable for aliens to thrive in Antarctic waters, there will be an extra front to defend: the ocean.
However, for aliens to invade by sea, they have to cross Earth's strongest current: the Antarctic Circumpolar Current. The ACC is a natural shield, rotating clockwise around the continent and kicking out any floating organisms that might find their way south. Humans, though, conquered the current more than a century ago.
Icebreaking vessels and tourist ships can navigate the treacherous waters, giving non-native species a chance to hitchhike from ports across the globe. "Ships that visit Antarctica visit every other part of the world, so potential pathways stretch everywhere," says Arlie McCarthy, a doctoral student at the University of Cambridge studying marine organisms in the Antarctic. Those pathways are becoming more well-traveled as time goes on, and they pose an increasing threat to Antarctica's fragile ecosystems.
In 2020, researchers discovered that mussels, originating from Patagonia, had settled in the Antarctic Peninsula. The species had arrived in Fildes Bay, on the West Antarctic peninsula, and was most likely brought in clinging to the hull of a ship. However, what kind of ship is hard to know. Over 50% of the vessels visiting the peninsula in recent years are filled with tourists. Another third arrive for scientific research. And both of these activities are increasing.
Warming waters have the potential to expose ecosystems that have been isolated for 25 million years, but it's notoriously hard to predict which species may invade and how damaging they'll be. "In many ways, we really don't know what the potential risks for Antarctica are," says McCarthy. The combination of unique species and isolation is unlike anything anywhere else in the world.
Read more: The Quest to Save Antarctica's Most Important Species
Even so, scientists are trying to understand which species are primed to invade. A group of Australian scientists, using a machine learning algorithm, were able to identify four marine species that could threaten the Antarctic marine ecosystem today and an additional five under future climate change scenarios. One species, the Northern Pacific seastar, is a particularly problematic invader. The starfish, which is native to the Northern Hemisphere, has invaded Tasmanian waterways – likely after being transported by a shipping vessel.
Scientists don't know exactly what kind of effects warming waters will have. There are encouraging results from the machine learning research, however. The risk of non-native species invading and establishing in Antarctic waters remains "very low" through to 2100 because the continent is just too cold and too far away. Surveillance and monitoring for any new arrivals remains paramount to keeping aliens out.
By the time RSV Nuyina crossed into the Antarctic Circle, the houseflies that snuck onto the ship during the first days of the voyage had disappeared.
Except for a few stowaways.
As the ship approached Casey Station, Australia's primary artery to the heart of Antarctica, I spotted a slow-moving fly sputtering against the rectangular windows on the observation deck. It buzzed and bashed against the glass as, outside, snow gently fell.
The ship's doctor, Brookes, handed me a paper coffee cup and, after a few fumbling attempts, I trapped the fly against the window. The doctor slid a piece of paper underneath and then, lightning-fast, we jammed a plastic lid over the cup. An alien, captured, now to be transported to containment in Nuyina's Area 51: the voyage leader's cabin.
When I peered into the room, the voyage leader was nowhere to be seen. I ran back upstairs carefully cradling the coffee cup and the captive fly and placed it on a table. I heard no buzzing or tapping. Looking through the drinking hole I found the fly was gone. Our alien had escaped.
There's zero chance this fugitive fly could cross the Antarctic tempest and settle on the eastern coast today, but the warmer climes of the Antarctic Peninsula reveal potential vulnerabilities and the difficulty of defending the near-pristine wilderness. Fourteen non-native species have been discovered on the peninsula, but their ability to establish, and the overall effects on the local ecosystem, is poorly understood.
If the aliens arrive, they'll need to be eradicated. Such a task could be exorbitantly expensive and difficult and might even disturb the local ecosystem more. Stopping an invasion before it begins seems to be the best form of mitigation, but is it impossible? Everywhere humans have stepped foot, we've carried aliens with us. The Antarctic is a special place with formidable barriers, but it isn't immune.
"We've been lucky so far," says Bergstrom, the ecologist from the Australian Antarctic Division. "But it won't stay that way."