Immense Greenland crater points to massive asteroid impact
Meteorologist/Science Writer
Thursday, November 15, 2018, 1:37 PM - An immense meteorite impact crater has been discovered in Greenland, astronomers have found compelling evidence for a massive planet orbiting Barnard's star, and the Gaia telescope has peered through the heart of the Milky Way and spotted a ghost galaxy on the other side. It's What's Up In Space!
FIRST METEORITE CRATER FOUND IN GREENLAND POINTS TO MASSIVE IMPACT
Earth is bombarded, daily, by tonnes of rocky, icy 'stuff' from space. Most of this 'stuff' just tiny flecks of dust and ice, that gets swept up without us even noticing it, with some larger bits mixed in that produce meteor streaks across the sky, and even the occasional fireball.
Every once in awhile, however, something far bigger gets in the planet's way. There are some famous ones - the immense comet or asteroid that produced the Chicxulub crater in the Gulf of Mexico, 66 million years ago, ending the reign of dinosaurs on the Earth, whatever it was (asteroid or comet) that exploded above Tunguska, Siberia, in June of 1908, flattening around 2,000 square kilometres of trees, and of course, the asteroid that exploded over Chelyabinsk, Russia, on February 15, 2013.
Just recently, an international team of scientists discovered the very first impact crater ever found in Greenland, and from the looks of it, the object that created it was an impressive meteoritic specimen.
This animation shows the Hiawatha glacier and the immense impact crater that lies beneath it. Credit: NASA Goddard Space Flight Center
This crater, located underneath the kilometre-thick ice of the Hiawatha Glacier, along the northwestern coast of Greenland, is roughly 31 kilometres wide! That puts it on the list of the 25 largest impact craters on the planet's surface!
According to the study, given the size and shape of the crater, and samplings of sediments from the river flowing out of the glacier, the asteroid that produced it was probably a rare iron asteroid, over one kilometre wide. The mass of such an object would have tipped the scales at around 4 billion metric tons, and it likely caused widespread climatic changes in the wake of the impact!
Also, although more study is required to lock down the age of this crater, the researchers currently estimate that it must have formed sometime after Greenland's current glaciers formed, due to how well preserved the formation is. That puts the timing of the impact sometime during last ice age, thus during the Pleistocene epoch - as early as 2.5 million years ago, up to as recently as 12,000 years ago.
"The crater is exceptionally well-preserved, and that is surprising, because glacier ice is an incredibly efficient erosive agent that would have quickly removed traces of the impact." says Professor Kurt H. Kjær from the Center for GeoGenetics at the Natural History Museum of Denmark, according to the University of Copenhagen.
"But that means the crater must be rather young from a geological perspective," Kjær added. "So far, it has not been possible to date the crater directly, but its condition strongly suggests that it formed after ice began to cover Greenland, so younger than 3 million years old and possibly as recently as 12,000 years ago - toward the end of the last ice age."
If this crater did form closer to the end of the Pleistocene epoch (and that is still a big IF at this time), it would be among the youngest impact craters on Earth, and it could - maybe - help solve a persistent mystery in the timeline of human culture and civilization.
Around 13,000 years ago, as glaciers in the northern hemisphere were in retreat, there was a sudden return to ice age conditions for a period of around 1,500 years, known as the Younger-Dryas period, which has been hypothesized as a cause of the disappearance of the Clovis culture from North America. Some studies have attributed this climate event to cold, fresh water pouring into the northern Atlantic Ocean, from a sudden melting of glacial ice, which would have shut down the warm Gulf Stream flow in the Atlantic, touching off a long-term cold spell across North America and Europe.
Further studies, looking for a possible cause of this sudden climatic shift, have pointed out that a comet or asteroid impact, somewhere in the Arctic Circle or across the glaciers that covered much of what is now Canada, could have produced such a sudden melting of glacial ice. Attempts to find anything to support the idea of such an impact did turn up some evidence, in the form of tiny 'microspherules' of iron and other materials discovered at Clovis dig sites, however counter-studies pointed to the lack of a major impact crater with the right age, to dispute this hypothesis.
Now, however, it would appear that such an impact crater has been found, at least if (and again, that is a very big IF at this time) the crater actually turns out to be that young.
(RELATED: Got your hands on a meteorite? Experts tell us how to know for sure!)
A NEW EXOPLANET NEIGHBOUR
Our stellar neighbourhood apparently has a new resident, or at the very least a resident that we have - after years of trying - finally been able to detect!
Barnard's star is a small red dwarf star, roughly one-fifth the size of the Sun, located just 6 light years away from us, and now, according to a team of astronomers, it is the parent star of newly discovered 'super-Earth' Barnard's star b.
According to the European Southern Observatory's press release:
The planet, designated Barnard's Star b, now steps in as the second-closest known exoplanet to Earth. The gathered data indicate that the planet could be a super-Earth, having a mass at least 3.2 times that of the Earth, which orbits its host star in roughly 233 days. Barnard's Star, the planet's host star, is a red dwarf, a cool, low-mass star, which only dimly illuminates this newly-discovered world. Light from Barnard's Star provides its planet with only 2% of the energy the Earth receives from the Sun.
Despite being relatively close to its parent star - at a distance only 0.4 times that between Earth and the Sun - the exoplanet lies close to the snow line, the region where volatile compounds such as water can condense into solid ice. This freezing, shadowy world could have a temperature of -170°C, making it inhospitable for life as we know it.
This frigid alien world, if it truly exists, is not only the second closest exoplanet to Earth, but it is also the closest exoplanet to Earth that orbits in a single-star system. Proxima Centauri b is closer, however its parent star is one of three stars in the Alpha Centauri system.
The closest stars to the Sun. Credit: NASA/Penn State University
The researchers involved in this detection are certainly confident in their findings. After all, they combined two decades worth of observations, and the input of over 60 different scientists from institutions and observatories around the world, producing what lead researcher Ignasi Ribas, from Spain's Institute of Space Studies of Catalonia and the Institute of Space Sciences, called "one of the largest and most extensive datasets ever used for precise radial velocity studies."
Even so, the 'if it truly exists' qualifier is still required for Barnard's star b, for now, simply because the planet's existence has not yet been confirmed by observations from other teams. There still remains a very small chance - less than 1 per cent - that what they've detected could be something from the star itself.
"After a very careful analysis, we are 99% confident that the planet is there," Ribas told the ESO. "However, we'll continue to observe this fast-moving star to exclude possible, but improbable, natural variations of the stellar brightness which could masquerade as a planet."
To find Barnard's star b, the international team combined 20 years worth of observations, using the 'Doppler method' of detecting exoplanets, which is also known as the 'wobble method'.
For the Doppler or 'wobble' method of planet-finding, astronomers carefully examine the light emitted by a star, watching for tiny regular shifts in the light's spectrum, back and forth between blue and red as the star is pulled towards us and away from us, again and again, by the gravity of an orbiting world.
Watch below to see how to use the Doppler or 'wobble' method to find alien worlds
(READ MORE: Catch up on the latest news about weather, climate and space from science writer Scott Sutherland, on The Weather Network's Out Of This World blog)
A 'GHOST GALAXY' LURKS
The European Space Agency's Gaia Telescope has been refining our place in the universe, by providing us with our best, most precise maps of the galaxy ever made, but recently it discovered something a little unexpected.
Lurking on the other side of the Milky Way Galaxy is an immense, dim 'ghost' galaxy named Antlia 2 (or Ant 2), in orbit around our home galaxy, but so far unnoticed and undetected by us here on Earth.
"This is a ghost of a galaxy," said Gabriel Torrealba, the lead author of the paper describing this discovery, according to a University of Cambridge news release. "Objects as diffuse as Ant 2 have simply not been seen before. Our discovery was only possible thanks to the quality of the Gaia data."
This composite image shows, left to right, the Large Magellanic Cloud, a representation of what the Milky Way Galaxy would look like from a distance, and the Antlia 2 'ghost' galaxy. Credit: V. Belokurov based on the images by Marcus and Gail Davies and Robert Gendler
According to the University of Cambridge:
Ant 2 is known as a dwarf galaxy. As structures emerged in the early Universe, dwarfs were the first galaxies to form, and so most of their stars are old, low-mass and metal-poor. But compared to the other known dwarf satellites of our Galaxy, Ant 2 is immense: it is as big as the Large Magellanic Cloud (LMC), and a third the size of the Milky Way itself.
What makes Ant 2 even more unusual is how little light it gives out. Compared to the LMC, another satellite of the Milky Way, Ant 2 is 10,000 times fainter. In other words, it is either far too large for its luminosity or far too dim for its size.
That's not the only strange things about Ant 2. In addition to being far too dim for its size, the dwarf galaxy also contains far less mass than it should for its size.
"The simplest explanation of why Ant 2 appears to have so little mass today is that it is being taken apart by the Galactic tides of the Milky Way," co-author Sergey Koposov explained. "What remains unexplained, however, is the object’s giant size. Normally, as galaxies lose mass to the Milky Way’s tides, they shrink, not grow."
The team suggests a few potential explanations for the size of this satellite galaxy, mostly involving dark matter - either the re-arranging of Ant 2's supply of the mysterious stuff, or possibly Ant 2 having an abundance of a different type of dark matter particle, not yet considered in models of galaxy formation.
"Compared to the rest of the 60 or so Milky Way satellites, Ant 2 is an oddball," co-author Matthew Walker added. "We are wondering whether this galaxy is just the tip of an iceberg, and the Milky Way is surrounded by a large population of nearly invisible dwarfs similar to this one."
Sources: Natural History Museum of Denmark | NASA | ESO | ESO Blogs | University of Cambridge
