Mystery of giant holes in Siberia

Huge holes have been discovered in a Siberian region nicknamed "the end of the world," reports the 'Siberian Times.' First a 260-foot-wide crater caught the world's attention in early July, and now researchers and reindeer herders have uncovered two more: one with a diameter of around 50 feet, and another — which nearly swallowed the herders who stumbled across it — with a diameter of only about 13 feet but an estimated depth of up to 328 feet, 'Gizmodo' reports.

This frame grab made on July 16, 2014, shows a crater discovered recently in the Yamal Peninsula in Yamalo-Nenets Autonomous Okrug, Russia.

Huge, mysterious gaping holes in Northern Siberia may not be such a mystery anymore. One scientist has pinned down a cause and, spoiler alert, it's not aliens or weapons testing, as had been theorized.

The first hole discovered in the Yamal Peninsula, which is 260 feet wide, is likely a sinkhole caused by melting ice or permafrost, University of Alaska geophysicist Vladimir Romanovsky tells LiveScience.

But rather than swallowing the earth as it opened up, he speculates, the hole "actually erupted outside," tossing dirt around the rim. (One caveat: Romanovsky hasn't seen the holes himself, but he has spoken to Russian colleagues who have, notes PRI.)

He suspects natural gas caused pressure to build as the water collected in an underground cavity, and the dirt—which is reportedly piled more than 3 feet high around the edge of the crater — was eventually expelled.

Plants around the crater suggests the hole is several years old, but closer inspection is needed to determine the exact age. Romanovsky thinks climate change played a role, which means "we will probably see this happen more often now," he says. But questions remain, notes LiveScience: Where did the natural gas come from, and why is the hole so even and round?

Early Earth could have been habitable

Hell on Earth: Despite being bombarded by 1000-kilometre wide asteroids, the environment of Earth could have been suitable for life, say researchers (Simone Marchi )

Stuart Gary
ABC

Isolated pockets of liquid water may have existed on the infant Earth even while it was being smashed by giant asteroids that boiled the oceans and created vast seas of magma, a new study suggests.

This means there could have been habitable regions on the Earth during its violent early period, say the authors in today's issue of the journal Nature.

But, they add, any life emerging during Earth's first half billion years would need to have been resistant to extreme conditions, and capable of spreading from the few stable niches existing at that time.

The constant mixing and burial of the Earth's crust by the unrelenting bombardment of asteroids, comets and meteors, during this Hadean epoch, means the geological history of this time -- and whether life existed then -- is poorly understood.

Dr Simone Marchi of the Southwest Research Institute, in Boulder Colorado, and colleagues, have developed a computer model that provides the most detailed picture yet of the Hadean epoch.
Some simulations show up to four large impacts involving 1000-kilometre wide asteroids capable of causing global sterilisation of any life existing at the time.

The simulations also found up to seven asteroids over 500 kilometres wide would have collided with the Earth, each capable of causing global ocean vaporisation, producing a steam atmosphere, and magma oceans, with the most recent occurring four billion years ago.

The researchers found every major part of the Earth would have been affected at one point or another.
Despite all this, the researchers say, there is evidence that there could have been habitable environments at the time.

"We found that the magma oceans were likely to be regional events, so at any given time there were some locations that were calm," says Marchi.

"That means liquid water could have existed in one place or another throughout the 500 million years of the Hadean period."

Marchi says the bombardment by 1000-kilometre wide asteroids would have completely wiped out any life existing at the time and, if that was the case, then life must have started over again after those large collisions.

Moon craters

Marchi and colleagues found the peak bombardment of the early Earth occurred soon after the formation of the Moon and gradually tapered off until the simulation ended 3.5 billion years ago, by which time the number of impacts was negligible.

They determined Earth's early impact history by examining the heavily cratered surface of the Moon which provides a record of the number of impact events and the size of the objects that caused them.

"The moon's surface is on average much older than the surface of the Earth, because the Moon is basically a dead body in which geological evolution is reduced to a minimal level," says Marchi.

"We found the populations of different sized impactors hitting the Moon is very similar to the size distribution of asteroids in the main asteroid belt today. This was also true for Mercury and the oldest surfaces on Mars."