Encounters with Jupiter send asteroid on a bizarre backward spin

by John Timmer, from ArsTechnica.com

Each time it approaches Jupiter, its orbit gets reset.

2015 BZ509 orbit jupiter

Credit: NASA

 

Jupiter is widely credited with providing Earth with a bit of protection. The immense gravity of the gas giant typically either sucks in asteroids and comets or flings them out into orbits where they pose our planet little danger. But astronomers have now identified an asteroid that’s in a stable orbital interaction with Jupiter. That interaction sends the asteroid around our Solar System backward and causes it to shift between two radically different orbits without ever settling into either.

The planets and other bodies in the Solar System mostly orbit in a single direction, inherited from the spinning disk of material from which they formed. A few bodies orbit in the opposite direction—called retrograde—but these tend to have odd, highly elliptical orbits. They’re also very rare; only 0.01 percent of the known asteroids have retrograde orbits. Orbiting in the wrong direction around the Solar System tends to bring an object into relative proximity to a planet twice an orbit, and the resulting gravitational interactions will eventually destabilize the orbit.

Or so we thought. Some mathematical work showed that it’s possible to have a stable retrograde orbit that overlaps with the orbit of a planet. In this case, the gravitational interactions are the key to stability. Each of the two passes of a single orbit would provide a nudge that counteracted the results of the previous one. While the orbit would shift with each nudge, it would remain stable due to this cancellation.

2015 BZ509 orbit jupiter

a, b, The motion of the asteroid as seen from above the plane of Jupiter’s orbit (a) and looking from the side along the plane of Jupiter’s orbit (b). Jupiter is indicated by the blue filled circle. Earth’s orbit is shown as a blue circle centred on the Sun (yellow filled circle) in a. The path of the asteroid is shown in red when the asteroid is above Jupiter’s orbital plane and in orange when it is below, from February 2018 until September 2029. The observational arc is shown in black.

Showing something’s mathematically possible, however, is different from showing that it happens. Nevertheless, with the theoretical background in place, people were excited by an asteroid discovered two years ago, called 2015 BZ509. It seemed to be in the right place to interact with Jupiter, and a very preliminary check of 2015 BZ509’s orbit suggested it might be moving in the wrong direction. So, a US-Canadian team of astronomers decided to get a careful look at its orbit.

While they did find that the asteroid was orbiting in a retrograde manner, they also found that Jupiter was giving it more than a nudge. Instead, the giant planet appears to act like a railway switch, getting 2015 BZ509 to alternate between two very different orbits.

After one pass with Jupiter, 2015 BZ509 gets shifted below the plane of the Solar System and sent on an orbit that brings it about half way between Jupiter’s orbit and that of Mars on its closest approach to the Sun. But the orbit is off-center from the Sun, meaning it swings farther out again, where the timing is such that it has a second encounter with Jupiter. When that takes place, 2015 BZ509 is flung above the plane of the Solar System and pushed into an orbit that has it loop out to about 1.5 times the Sun-Jupiter distance.

Amazingly, this is all stable. The authors calculate that the cycle can continue for at least a million years, and quite possibly longer.

What’s less clear is how any body could have ended up falling into this sort of arrangement in the first place. The authors suspect an interaction with both Jupiter and Saturn could have pushed a body into the right location for Jupiter to take over. And, based on that location, it would probably be a comet. But the asteroid shows no sign of comet-like behavior during its closest approach to the Sun. So the identity of 2015 BZ509 remains a mystery.

But its orbit is no longer a mystery, even if it is rather odd.

 

Asteroid 2015 BZ509 always remains in the vicinity of Jupiter’s orbit, and does not approach the Earth. The asteroid is not considered hazardous to our planet.

Nature, 2017. DOI: 10.1038/nature22029

Original article here.

Did an asteroid trigger ancient tsunamis on Mars?

by Weston Williams, from The Christian Science Monitor

A team of researchers found that certain geological features on the Red Planet indicate that the impact that created the Lomonosov crater may have also created massive waves in an ancient Martian sea.

Lomonosov crater Mars asteroid tsunami

Mars. Image: NASA

A team of scientists believes that an asteroid impact at the site of Mars’ Lomonosov crater may have been responsible for the massive tsunamis thought to have swept the region three billion years ago.

Scientists have hypothesized before that asteroid impacts could have created tsunamis during Mars’ watery past. But this is the first time a specific crater has been tied to a specific tsunami on the Red Planet.

While many scientists say that the Martian surface was covered with water, the extent of that coverage is still widely debated. During the course of the study, the researchers noticed that certain lobate deposits, frequently associated with water movement on ancient Mars, seemed to have flowed into the southern region of the planet from where a northern ocean would have been located.

“We found typical tsunami deposits along the dichotomy between the northern hemisphere and southern hemisphere of Mars,” François Costard, lead author of a study on the event, told the BBC. “It supports [the idea] that there was, at that time, a northern ocean.”

The giveaway was a set of geological formations that look like the ridges in a human fingerprint – but on a much larger scale.

“There’s…[a] set of landforms that we see along the coastline called thumbprint terrain,” Stephen Clifford, study co-author, told the BBC. “The reflection of the tsunami waves from the coast and their interaction with a second set of tsunami waves, predicted by the numerical modeling, would have resulted in sediment deposition that’s very similar to what we actually observe on Mars.”

According to the study, published in the Journal of Geophysical Research—Planets, the source of these tsunami features was one of a few possible asteroid impacts that could have hit the northern ocean at the time. But the most likely culprit was the explosive impact that created the 75-mile-wide Lomonosov crater.

“It was a really large-scale, high speed tsunami,” said Dr. Costard. “At the very beginning, a crater of 70 kilometers [43.5 miles] in diameter was created by the impact. This expelled a huge volume of water, with wave propagation at 60 meters per second [134 miles per hour]. The initial wave was about 300 meters [984 feet] in height. After just a few hours, that tsunami wave reached the paleo-shoreline located at a few hundred kilometers from the impact crater.”

The impact would have created two separate waves, leaving deposits as far away as 95 miles inland with wave heights of about 330 feet.

Lomonosov crater Mars asteroid tsunami

The Frosted Craters of Northern Spring and Southern Autumn – Lomonosov Crater (Image: NASA)

“It’s very hard to conceive of any other process other than a tsunami that could have emplaced these lobate deposits along the dichotomy boundary,” Dr. Clifford told the BBC. “There is ambiguity in all the various lines of evidence that have been cited regarding whether Mars is water-rich or water-poor. But the morphologic evidence that’s been presented here is a very persuasive case for a water-rich planet.”

And if Mars was once able to support oceans of water, as this study would indicate, it is possible that the Red Planet might have been able to support life as well.

“If we do have this evidence of a tsunami having occurred back three billion years ago, there must have been an ocean present in the northern plains,” said Clifford. “That’s the key point here, it indicates that there was a substantial amount of water in residence on the Martian surface at this time and that has likely implications for the total inventory of water on Mars.”

Original article here.

 

Blue fireball lights up sky over Sweden

A very large blue fireball illuminated the sky over Sweden around 20:30 UTC (21:30 CET) on March 20, 2017. The event was so powerful that the whole sky lit up, Swedish All Sky Meteor Network astronomers said.

blue fireball Sweden 2017

Credits: Jessica Dellsjö

Images of the event immediately started appearing on social networks, with people from the cities of Stockholm, Uppsala and Örebro all reported seeing the event. Reports from eastern Uppland mention sonic boom associated with the event. 

Several cameras from the Finnish Meteor Network have also registered the event.

Eric Stempels, from the Department of Physics and Astronomy at Uppsala University, has reassured the public that the fireball was harmless, and that this phenomena is perhaps more common than people think.

“This was something very small that does not pose any threat to us,” said Stempels.  “This is something that happens a few times a year.”

“Because it can happen during the day, when it is cloudy or far from populated areas, these events usually don’t get much attention,” he said, adding that this one fell in the north-eastern Uppland region.

Credits: Jessica Dellsjö

Stempels estimates that the size of the object was between the size of a “fist and a football,” and according to the Swedish Allsky Media Network, its blue coloration was caused by a combination of speed and a majority of magnesium in its composition.

One of the Swedish Allsky Meteor Network‘s cameras in Uppsala managed to capture the bright light. Watch the short video below:

“By combining Finnish observations with the Swedish reports, it is clear that it was a space rock that burned up in the atmosphere. It came from the east and was moving almost due west of northeastern Uppland. The bolide first appeared at an altitude of about 90 km (60 miles), and stopped shining at an altitude of about 35 km (21.7 miles),” Swedish AllSky Meteor Network astronomers explained. 

“It was truly a wonderful sight,” Mikko Suominen of the Finish Meteor Network said.

Sources:
Mystery blue fireball lights up Swedish night sky, by The Local
Large blue meteor fireball illuminates sky over Sweden, by Sott.net
Blue Fireball Lights Up Sky Over Sweden, by The Singular Fortean Society

Ancient Platinum Asteroid Wiped Out Native American Civilization

By Peggy Binette, University of South Carolina

No one knows for certain why the Clovis people and iconic beasts — mastodon, mammoth and saber-toothed tiger — living some 12,800 years ago suddenly disappeared. However, a discovery of widespread platinum at archaeological sites across the U.S. by three University of South Carolina archaeologists has provided an important clue in solving this enduring mystery.

clovis people platinum

The discovery of an abundance of platinum at Clovis sites across the U.S. adds to the research that suggests a cosmic event may have wiped out the Clovis people and large beasts that lived around 12,800 years ago. Photo courtesy of NASA.

The research findings are outlined in a new study released Thursday (March 9) in Scientific Reports, a publication of Nature. The study, authored by 10 researchers, builds on similar findings of platinum — an element associated with cosmic objects like asteroids or comets — found by Harvard University researchers in an ice-core from Greenland in 2013.

The South Carolina researchers found an abundance of platinum in soil layers that coincided with the “Younger-Dryas,” a climatic period of extreme cooling that began around 12,800 years ago and lasted about 1,400 years. While the brief return to ice-age conditions during the Younger-Dryas has been well-documented by scientists, the reasons for it and the demise of the Clovis people and animals have remained unclear.

“Platinum is very rare in the Earth’s crust, but it is common in asteroids and comets,” says Christopher Moore, the study’s lead author and an archaeologist at Carolina. He calls the presence of platinum found in the soil layers at 11 archaeological sites in California, Arizona, New Mexico, Ohio, Virginia, North Carolina and South Carolina an anomaly.

“The presence of elevated platinum in archaeological sites is a confirmation of data previously reported for the Younger-Dryas onset several years ago in a Greenland ice-core. The authors for that study concluded that the most likely source of such platinum enrichment was from the impact of an extraterrestrial object,” Moore says.

“Our data show that this anomaly is present in sediments from U.S. archaeological sites that date to the start of the Younger-Dryas event. It is continental in scale — possibly global — and it’s consistent with the hypothesis that an extraterrestrial impact took place.”

He says the Younger-Dryas coincides with the end of Clovis culture and the extinction of more than 35 species of ice-age animals. Moore says while evidence has shown that some of the animals were on the decline before Younger-Dryas, virtually none are found after it.

Moore says that would indicate an extinction event for North America.

He also says the platinum anomaly is similar to the well-documented finding of iridium, another element associated with cosmic objects, that scientists have found in the rock layers dated 65 million years ago from an impact that caused dinosaur extinction. That event is commonly known as Cretaceous-Tertiary or K-Pg by scientists.

“In both cases, the anomalies represent the atmospheric fallout of rare elements resulting from an extraterrestrial impact,” Moore says.

He says the K-Pg dinosaur extinction was the result of a very large asteroid impact while the Younger-Dryas onset impact is likely the result of being hit by fragments of a much smaller sized comet or asteroid, possibly measuring up to two-thirds a mile in diameter.

“Another difference is that the Younger-Dryas impact event is not yet associated with any known impact crater,” Moore says. “This may be because the fragments of the large object struck the glacial ice-sheet or exploded in the atmosphere. Several candidate craters are under investigation but have not been confirmed.”

Moore says while his team’s data does not contradict the Young-Dryas impact hypothesis, it also does not explain the likely effects that such an impact could have had on the environment, Paleoindians or ice-age animals.

clovis people platinum

UofSC archaeologists Christopher Moore, Albert Goodyear and Mark Brooks were among a research team that found concentrations of platinum, an element rarely found on the earth’s crust, at 11 U.S. Clovis excavation sites.

Contributing to the study are Moore’s university colleagues Mark Brooks, a geo-archaeologist who conducts research and excavations at the Savannah River Site, and archaeologist Albert Goodyear, who has spent decades documenting Clovis culture at the famed Topper site. Topper, located in Allendale County, South Carolina, along the banks of the Savannah River, is considered one of the most pristine U.S. sites for research on Clovis, one of the earliest ancient people.

Goodyear’s work with Moore builds on research in which he found traces of extraterrestrial elements, including iridium, at the Younger-Dryas layer at Topper that was published in the Proceedings of the National Academy of Sciences in 2012.

Moore, Goodyear and Brooks conduct research through the South Carolina Institute of Anthropology and Archaeology in the university’s College of Arts and Sciences.

In addition to Topper, the remaining 10 archaeological sites that Moore, Goodyear and others on their team conducted research in 2016 included Arlington Canyon on Santa Rosa Island, California; Murray Springs, Arizona; Blackwater Draw, New Mexico; Sheriden Cave, Ohio; Squires Ridge and Barber Creek, North Carolina; and Kolb, Flamingo Bay, John Bay and Pen Point, South Carolina.

Moore says the bottom line of the study and paper in the journal Scientific Reports is the presence of an easily identifiable hemispheric marker (platinum) in sediment layers for the start of Younger-Dryas. That discovery contributes to the body of evidence that a potential cosmic impact event occurred and warrants further scientific investigation. 

Original press release here.