Dead – yes, dead – tardigrade found beneath Antarctica

A completely unexpected discovery beneath the ice.

Dead – yes, dead – tardigrade found beneath Antarctica
(Goldstein Lab/Wkikpedia/Tigerspaws/Big Think)
  • Scientists find remains of a tardigrade and crustaceans in a deep, frozen Antarctic lake.
  • The creatures' origin is unknown, and further study is ongoing.
  • Biology speaks up about Antarctica's history.

So it turns out our favorite real-world superheroes, tardigrades, aren't completely indestructible. But even in death, they continue to amaze. Scientists boring a hole one kilometer beneath the ice deep within a buried Antarctic lake recently got a bit of a shock. They came across the remains of once-living creatures, some ancient crustaceans, and — you guessed it — a water bear. How all of the creatures got there remains unclear.

The discovery was "completely unexpected," micropaleontologist David Harwood tells Nature. The drilling was done under the auspices of the SALSA (Subglacial Antarctic Lakes Scientific Access) project. Glaciologist Slawek Tulaczyk, who's not involved with SALSA, says, "This is really cool. It's definitely surprising."

Welcome to Subglacial Lake Mercer

The scientists were drilling in Subglacial Lake Mercer, a frozen body of water undisturbed for millennia. SALSA's is the first direct sampling of its contents. Prior to the drilling, it had only been examined with ice-penetrating radar and some other indirect detection devices.

Boring details

SALSA drilled down a kilometer into the ice above Lake Mercer using a hot-water drill . At its maximum width, the hole was just 60 centimeters across.

On December 30, the team retrieved a temperature sensor from the frozen lake and noticed some gray-brown mud stuck to the bottom of it. Looking at the mud under a microscope, Harwood saw the glassy remains of photosynthetic diatoms, which he expected, but also a shrimp-like crustacean shell with its legs still intact. And then another, even better-preserved one.

To double-check, the team cleaned off their sensor and sent it down for more mud. This time, more crustacean shells and some other things that looked a bit like worms appeared under the microscope. On January 8, at a National Science Foundation base 900 kilometers away, animal ecologist named Byron Adams had a look. He confirmed the crustaceans, found the tardigrade, and identified the worm-like organisms as being thread-like plants or fungi. He'd seen all three types of creatures previously in the glacier-free Dry Valleys of Antarctica, as well as in the Transantarctic Mountains.

Where the organisms were found, but why?

The animals could have come from other places, such as the ocean. Between five and ten thousand years ago, the Antarctic ice sheet became thinner for a while, and this could have allowed seawater to make its way beneath floating ice, carrying organisms along with it that eventually became trapped beneath the ice sheet when it returned to its normal thickness.

The water sampled from Lake Mercer has enough oxygen to sustain life, and is packed with bacteria, over 10,000 cells per millimeter. Harwood wonders if larger animals could have survived feeding on them, though the majority of biologists don't think it's likely to have been a substantial enough food source.

Adams suspects the creatures actually lived in the Transantarctic Mountains and were then transported after dying down to Lake Mercer. He says they seem too recent to have been neighbors of the millions-of-years-old diatoms. "What was sort of stunning about the stuff from Lake Mercer," Adams tells Nature, "is it's not super, super-old. They've not been dead that long." The eight-legged tardigrade from Lake Mercer resembles those found in damp soil, reinforcing Adam's conclusion.

Back to the lab

The next steps for these intriguing remains is an attempt at determine their age using radiocarbon dating. In addition, researchers will try and sequence DNA scraps from them to learn if they're of marine or freshwater species. Finally, scientists will perform chemical analyses of carbon the remains contain to see if a determination can be made as to whether the animals spent their days in sunlight or in the dark, far beneath the Antarctic.

This is what aliens would 'hear' if they flew by Earth

A Mercury-bound spacecraft's noisy flyby of our home planet.

Image source: sdecoret on Shutterstock/ESA/Big Think
Surprising Science
  • There is no sound in space, but if there was, this is what it might sound like passing by Earth.
  • A spacecraft bound for Mercury recorded data while swinging around our planet, and that data was converted into sound.
  • Yes, in space no one can hear you scream, but this is still some chill stuff.

First off, let's be clear what we mean by "hear" here. (Here, here!)

Sound, as we know it, requires air. What our ears capture is actually oscillating waves of fluctuating air pressure. Cilia, fibers in our ears, respond to these fluctuations by firing off corresponding clusters of tones at different pitches to our brains. This is what we perceive as sound.

All of which is to say, sound requires air, and space is notoriously void of that. So, in terms of human-perceivable sound, it's silent out there. Nonetheless, there can be cyclical events in space — such as oscillating values in streams of captured data — that can be mapped to pitches, and thus made audible.

BepiColombo

Image source: European Space Agency

The European Space Agency's BepiColombo spacecraft took off from Kourou, French Guyana on October 20, 2019, on its way to Mercury. To reduce its speed for the proper trajectory to Mercury, BepiColombo executed a "gravity-assist flyby," slinging itself around the Earth before leaving home. Over the course of its 34-minute flyby, its two data recorders captured five data sets that Italy's National Institute for Astrophysics (INAF) enhanced and converted into sound waves.

Into and out of Earth's shadow

In April, BepiColombo began its closest approach to Earth, ranging from 256,393 kilometers (159,315 miles) to 129,488 kilometers (80,460 miles) away. The audio above starts as BepiColombo begins to sneak into the Earth's shadow facing away from the sun.

The data was captured by BepiColombo's Italian Spring Accelerometer (ISA) instrument. Says Carmelo Magnafico of the ISA team, "When the spacecraft enters the shadow and the force of the Sun disappears, we can hear a slight vibration. The solar panels, previously flexed by the Sun, then find a new balance. Upon exiting the shadow, we can hear the effect again."

In addition to making for some cool sounds, the phenomenon allowed the ISA team to confirm just how sensitive their instrument is. "This is an extraordinary situation," says Carmelo. "Since we started the cruise, we have only been in direct sunshine, so we did not have the possibility to check effectively whether our instrument is measuring the variations of the force of the sunlight."

When the craft arrives at Mercury, the ISA will be tasked with studying the planets gravity.

Magentosphere melody

The second clip is derived from data captured by BepiColombo's MPO-MAG magnetometer, AKA MERMAG, as the craft traveled through Earth's magnetosphere, the area surrounding the planet that's determined by the its magnetic field.

BepiColombo eventually entered the hellish mangentosheath, the region battered by cosmic plasma from the sun before the craft passed into the relatively peaceful magentopause that marks the transition between the magnetosphere and Earth's own magnetic field.

MERMAG will map Mercury's magnetosphere, as well as the magnetic state of the planet's interior. As a secondary objective, it will assess the interaction of the solar wind, Mercury's magnetic field, and the planet, analyzing the dynamics of the magnetosphere and its interaction with Mercury.

Recording session over, BepiColombo is now slipping through space silently with its arrival at Mercury planned for 2025.

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