another “lost treasure” due to global warming
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In an increasingly warming world, there is an additional problem that no one, or almost no one, has thought about: as the ice becomes softer, many of the meteorites on it in the polar regions, especially Antarctica, are sinking hopelessly, disappearing from view and thereby depriving scientists one of the best existing sources of direct information on the history of the solar system.
Recent studies have shown that about 17,000 meteorites weighing more than 50 grams, large enough to be found and analyzed, fall to Earth each year. The rest, the vast majority, dissolve when they enter the atmosphere and fall out as dust, that is, invisible to any search engine. In total, between rocks and dust, the “extraterrestrial” contribution to the Earth’s mass is estimated at about 40,000 tons per year.
Most of the 17,000 meteorites that resist penetration and fall as rocks (weighing from a few grams to a few kg) each year end up in the sea that covers 70% of the planet’s surface, and it has been estimated that most of them do so in the area between 45 degrees north and south of the equator.
But it turns out that almost all the meteorites at the disposal of researchers were discovered far away, in Antarctica. And not because there are more of them on the frozen continent, but because the dark colors of these extraterrestrial rocks stand out against the background of white ice and are visible even at great distances. In total, numerous expeditions over several decades have already discovered about 48,000 Antarctic meteorites.
The end of plenty
But this may not last long. In fact, a detailed analysis in the journal Nature of Climate Change by a team of researchers from Belgium and the United Kingdom suggests that global temperature rises are “softening” large masses of Antarctic ice, meaning meteorites are sinking into them, beyond our reach. Over the next few decades, the study concludes, we could lose up to 5,000 meteorites a year this way: a veritable treasure trove of information of incalculable value from both the solar system and interstellar space.
The truth is that meteorites are an incomparable resource for studying and better understanding our little corner of the Milky Way. In fact, they consist mainly of fragments of asteroids formed at the dawn of the solar system (about 4.5 billion years ago), or from pieces of other planets (such as Mars, Venus or Mercury) or even our own Moon, which they were torn from their home worlds due to strong impacts, and were then launched in our direction. Some even contain materials so old that they predate the formation of the solar system itself.
Therefore, these pieces of black rock on white ice have turned Antarctica into an ideal “hunting spot” for meteorite hunters. Where terrestrial rocks are scarce, it is highly likely that any rock we see on the ice came from outer space. Antarctica’s cold, dry desert environment also helps meteorites better preserve their original state, even if they fell a long time ago.
Space rocks found in Antarctica finally provide not only small databases of information about other worlds or the early solar system, but also help scientists determine the speed at which they reached Earth, which is of paramount importance in creating planetary defense mechanisms.
“Treasure” that is about to be lost
On average, various scientific expeditions annually extract about 1,000 meteorites from Antarctica. Glaciologists Veronica Tollenaar of the Vrije Universiteit Brussels and Harry Zekollari of ETH Zürich, who led the study, had already estimated in previous work that the frozen continent could be “strewn” with between 300,000 and 850,000 different meteorites. many of them fell more than a million years ago. However, estimates now indicate that much of this “cosmic treasure” is about to be lost because the rocks will not remain where they fell for long.
It is already known from previous studies that the population of Antarctic meteorites is very sensitive to temperature. Tollenaar and Zekollari themselves have, in fact, already shown that almost no meteorites have been found in areas where surface temperatures exceed 9 degrees below zero, even if they do so for short periods of time. Models also show that meteorites can sink into ice at temperatures above -10 degrees.
Using this data, the researchers used a machine learning algorithm to calculate how many meteorites would be lost and buried in ice as temperatures rise. And they found that even if we take into account the most conservative rates of warming, we will inevitably lose thousands of meteorites per year.
Diagram of the mechanism of meteorite concentration with the entry of meteorites through an ice stream (black arrows) and direct fall and loss of meteorites due to melting from the surface (red arrows)
Veronica Tollenaar, Harry Zekollari and others/Nature, climate change
If warming reaches the predicted 2.7 degrees above pre-industrial levels, 28 to 30 percent of Antarctic meteorites could be lost by 2050. In some regions this number can be as high as 50 percent; and in the highest emissions scenarios, with warming 5.2 degrees above pre-industrial levels, up to 76 percent of Antarctic meteorites would be permanently buried under ice by 2100.
“The ongoing loss of Antarctic meteorites,” the researchers write, “is a consequence of climate change. That’s why rapid and targeted collection of all possible meteorites is necessary to preserve the information about our solar system that each additional sample contains: for example, information about the emergence of life on Earth through the influx of water and organic matter and how the Moon was formed. The concerted effort would be similar in spirit to what is now being done in ice core research, where ice samples collected from vanished but unique glaciers, such as the few remaining tropical glaciers, are stored in long-term archives. “Ultimately, however, the only way to preserve the remaining unrecovered Antarctic meteorites is to rapidly reduce greenhouse gas emissions.”