A giant crater under the Hiawatha Glacier formed much sooner than we thought

(ORDO NEWS) — A huge impact crater lurking deep under Greenland’s Hiawatha Glacier is likely the result of a kilometer-wide asteroid that crashed into Earth 58 million years ago.

When Hiawatha Crater was first discovered in 2015, researchers suspected it was formed by a meteorite impact somewhere between 12,000 years and 3 million years ago.

These dates roughly correspond to the last ice age, and judging by the state of the crater, the asteroid that formed it seems to have crashed into an already formed ice sheet.

However, these conclusions were based on circumstantial evidence such as GPR scans. In the years since the 31 km wide depression was first discovered, researchers have been trying to figure out its true age.

The task is not easy, given that most of the crater lies under a kilometer-long layer of ice. However, using two different dating methods, two groups of scientists from Denmark and Sweden came to almost the same conclusions and published their results this week.

“The determination of the new age of the crater surprised us all. I am convinced that we have determined the actual age of the crater, which is much older than people ever thought.” – Michael Storey, geologist at the Natural History Museum of Denmark

The evidence scientists have found is based on specimens found along the banks of rivers downstream of the Hiawatha Glacier, which carry stones and sand from bedrock under the ice sheet into the open. It is these molten rock samples that can be used to date the cosmic impact.

In Sweden, researchers at the National Museum of Natural History have focused on coastal rocks containing the mineral zircon. When this mineral is impacted by a meteorite, it forms new crystals that include the radioactive element uranium but exclude lead. Thus, the ratio of uranium to lead can show the age at which this crystallization began.

In Denmark, the researchers relied on a method called argon dating. By heating sand collected downstream of the glacier with a laser, the team isolated argon gas from individual grains. The isotopes of this gas were then used to determine how much radioactive decay had occurred since the minerals were melted by the meteorite impact.

As a result, scientists from Denmark have determined the date of the impact of the asteroid between 56 and 66 million years ago, while the Swedish researchers have narrowed the date to 58 million years ago.

Hiawatha Crater is nearly six times smaller than Mexico’s infamous Chicxulub Crater. This means that it could not lead to such catastrophic consequences as the extinction of dinosaurs 8 years before.

However, the fall of this asteroid had an impact on the surface of our ancient planet a million times more powerful than an atomic bomb could have. Thus, it was quite capable of influencing the local or even global climate of that time.

In the late Pleistocene, Greenland looked very different from what it is today. This island was probably covered in rainforest, and many species of flora and fauna flourished in the temperate climate. Researchers are currently studying how the Hiawatha crater meteorite may have changed this ecosystem and its climate millions of years ago.

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