Meteor

Meteor crater discovered hidden by polar ice

James Guilford , , ,
Animated GIF: Credit: NASA's Goddard Space Flight Center/Cindy Starr
Two views of the Hiawatha crater region: one covered by the Greenland Ice Sheet, and the second showing the topography of the rock beneath the ice sheet, including the crater. Credit: NASA’s Goddard Space Flight Center/Cindy Starr

An international team of researchers that includes a NASA glaciologist has discovered a 19-mile-wide meteorite impact crater hiding beneath more than half a mile of ice in northwest Greenland. This is the first impact crater of any size ever found under the polar ice sheets.

The group, led by researchers from the Centre for GeoGenetics at the Natural History Museum of Denmark, University of Copenhagen, worked for the past three years to verify their discovery, which was initially made in 2015 using NASA data. The researchers first spotted the crater in July 2015, while they were inspecting a new map of the topography beneath Greenland’s ice sheet that used ice-penetrating radar data primarily from NASA’s Operation IceBridge — a multi-year airborne mission to track changes in polar ice — and earlier NASA airborne missions in Greenland. The scientists noticed an enormous, previously unexamined circular depression under Hiawatha Glacier, sitting at the very edge of the ice sheet in northwestern Greenland.

Their finding is described in a study published on Nov. 14 in the journal Science Advances. The crater is roughly 1,000 feet deep and more than 19 miles in diameter, encompassing an area slightly larger than that comprised inside the Capital Beltway around Washington, D.C. Its dimensions place it among the 25 largest impact craters on Earth.

The crater formed when an iron meteorite more than half a mile wide smashed into northwest Greenland – but the timing of when the event happened remains a key question and one the researchers want to answer next. The authors put the range between less than three million years ago and as recently as less than 13,000 years ago. The resulting depression has since been covered by ice.

A narrated video outlines the discovery and includes data visualizations which can be found here: https://svs.gsfc.nasa.gov/4572

2018 Perseids meteor shower

James Guilford , , , , , , , , , , , , , , , ,
Photo: Perseids Composite: Images combined to show 22 meteors viewed from Salt Fork State Park, Ohio. Photo Credit: Frank Shoemaker.
Perseids Composite: Images combined to show 22 meteors and radiant direction, viewed from Salt Fork State Park, Ohio. Photo Credit: Frank Shoemaker.

Note: This post will be updated with additional photos and narrative as provided by CAA members.

The 2018 occurrence of the annual Perseids meteor shower was not particularly outstanding but among sky watchers the event’s timing offered some promise; it peaked on a weekend and Earth’s Moon offered no interference! Overall, members enjoyed the experience but were not impressed by the Perseids’ performance!

A few intrepid members of the Cuyahoga Astronomical Association (CAA) spent late nights into early mornings at darker sites around the area ranging from Observatory Park in Geauga County, to Letha House Park in Medina County, Findley State Park in Lorain County, and Salt Fork State Park in Guernsey County.

Photo: The night wasn't stellar Saturday for the 2018 Perseids Meteor Shower as viewed from Letha House Park West, Medina County. This fisheye view of observers leaving at 12:35 AM. Photo Credit: James Guilford.
The night wasn’t stellar Saturday for the 2018 Perseids Meteor Shower as viewed from Letha House Park West, Medina County, as clouds and light pollution hindered observations. This fisheye view of observers leaving at 12:35 AM. Photo Credit: James Guilford.

Saturday night observers were largely frustrated by clouds moving over the Northern Ohio area though some did report seeing meteors. The passing clouds were illuminated not only by city light pollution but also by flashes of lightning from thunderstorms over Lake Erie!

Member Lonnie Dittrick, out Saturday night, reported, “Spent about 2.5 hours out near Wellington and snagged 23 meteors (about 1 every 9.6 minutes). Conditions fair with lots of high clouds and a cloud-out for 30 minutes. Reoccurring lighting north over the lake. Three very bright shooters that left trails. 11:10 to 1:40 AM.”

Joining the crowd at Observatory Park, Nancy Whisler wrote, “We counted 34 up until midnight, then we left because it was getting so cloudy and moist. We had a great time!”

Some folks tried watching from their own back yards. “Stayed home in Brunswick on my backyard patio Saturday night and Sunday,” wrote Jon Salontay. “Saturday started out with promising skies and weather but the sky got very hazy and smoky early and cloudy later. Saw only one sporadic meteor around midnight and didn’t catch any with my camera. Limiting magnitude was at best 3rd magnitude, probably 2nd. Sunday night saw better conditions; much darker and clearer.”

“Saw only two Perseids though: one early at 11:30 PM, and another around 4 AM, in an early and later session. Three meteors, in two days, in five hours observing.” Reflecting the feelings of many observers, Salontay concluded, “I’ve had better nights.”

Watching from his home’s deck in Brunswick Hills, Matt Franduto wrote, “The last two nights (2 – 3:00 AM) have been awful. Zero on Friday. Three (Saturday) night.”

Sunday night, inconvenient for many due to Monday work schedules, offered better skies and a nice selection of fireballs (exceptionally bright meteors) in addition to more ordinary “shooting stars.”

Watching the sky from “the lovely skies of North Olmsted,” was Steve Korylak. “I took about 200 15-second exposures covering Cygnus and Cassiopeia starting at 1:30 AM and caught not 0ne. However the next half-hour I saw three Perseids and four sporadics. Some shower, more like a drizzle!”

Photo: Sword of Mars: A Perseid fireball meteor streaks past the brilliant planet Mars in the skies over Findley State Park, Wellington, August 12, 2018, 1:03 AM. Photo Credit: James Guilford.
Sword of Mars: A Perseid fireball meteor streaks past the brilliant planet Mars in the skies over Findley State Park, Wellington, August 12, 2018, 1:03 AM. Photo Credit: James Guilford.

From Findley State Park, James Guilford watched and photographed from twilight until 1:30 AM Saturday to Sunday. He did not keep count as photography was his main interest. “I saw a few dim Perseids and several fireballs and captured one as it passed Mars,” he wrote. “The main problem became dew; one after another the camera lenses fogged up and I had to keep swapping them out. The camera and tripod were dripping wet by the time I had to call it quits!”

Dark skies matter when it comes to spotting meteors. Member Frank Shoemaker, who went to Salt Fork, reported, “My daughter and I went down to Salt Fork state park and were out from 11:30 PM to 4:30 AM on Sunday night/Monday morning. The clouds completely cleared out about 1:30 AM and we eventually lost count of Perseids in the 70s. I think we saw at least 80 of them.” That was a good night! See his composite photo at top of this story.

Photo: Singular Streak: A close-up view of a Perseid as it passed through constellation Cassiopeia Sunday morning. Photo Credit: John D. Burkett.
Singular Streak: A close-up view of a Perseid as it passed through constellation Cassiopeia Sunday morning. Photo Credit: John D. Burkett.

Member John Burkett took a different approach in making his meteoric image: as an experiment he attached cameras to a CGEM which tracked with background stars. The image above was produced from a Nikon D810, Nikon 35mm f/1.4 @ f/4, ISO-200, single-frame 76-Seconds, cropped. It was just below and to the right of the big “W”. He was three miles out of Seville, time stamp is 5:29 AM.

 

“Beautiful” fireball seen, recorded

James Guilford , , , ,
Photo: June 11, 2016 Meteor Track - Credit: NASA
June 11, 2016 – 10:17 PM EDT Fireball meteor captured by NASA’s All-Sky Fireball Network located at Hiram College. Credit: NASA

Kim Doran emailed us on June 12 asking if anyone had seen what she witnessed the night before: a brilliant, multi-colored fireball meteor. Fireballs are meteors that flare to become brighter than the planet Venus.

We don’t know if other human observers saw the meteor’s brilliant fall but NASA’s automated cameras on the campuses of Hiram College and Oberlin College recorded the June 11 event at 10:17 PM EDT.

“(I) saw what I thought was a very large shooting star … then brighter flash and very thick trail with quick red, bright white, and some blue.” She said she is 57 years of age and has never seen anything quite like this before. “Beautiful!”

Crucial data gained from Chelyabinsk meteor fall

James Guilford , , , , ,

News from NASA….

A team of NASA and international scientists for the first time have gathered a detailed understanding of the effects on Earth from a small asteroid impact.

The unprecedented data obtained as the result of the airburst of a meteoroid over the Russian city of Chelyabinsk on Feb. 15, has revolutionized scientists’ understanding of this natural phenomenon.

The Chelyabinsk incident was well observed by citizen cameras and other assets. This factor provided a unique opportunity for researchers to calibrate the event, with implications for the study of near-Earth objects (NEOs) and the development of hazard mitigation strategies for planetary defense. Scientists from nine countries now have established a new benchmark for future asteroid impact modeling.

“Our goal was to understand all circumstances that resulted in the shock wave,” said meteor expert Peter Jenniskens, co-lead author of a report published in the journal Science.

Jenniskens, a meteor astronomer at NASA’s Ames Research Center and the SETI Institute, participated in a field study led by Olga Popova of the Institute for Dynamics of Geospheres of the Russian Academy of Sciences in Moscow in the weeks following the event.

“It was important that we followed up with the many citizens who had firsthand accounts of the event and recorded incredible video while the experience was still fresh in their minds,” said Popova.

By calibrating the video images from the position of the stars in the night sky, Jenniskens and Popova calculated the impact speed of the meteor at 42,500 mph (19 kilometers per second). As the meteor penetrated through the atmosphere, it fragmented into pieces, peaking at 19 miles (30 kilometers) above the surface. At that point the superheated meteor appeared brighter than the sun, even for people 62 miles (100 kilometers) away.

Because of the extreme heat, many pieces of the meteor vaporized before reaching Earth. Scientists believe that between 9,000 to 13,000 pounds (4,000 to 6,000 kilograms) of meteorites fell to the ground. This amount included one fragment weighing approximately 1,400 pounds (650 kilograms). This fragment was recovered from Lake Chebarkul on Oct. 16 by professional divers guided by Ural Federal University researchers in Yekaterinburg, Russia.

NASA researchers participating in the 59-member consortium study suspect the abundance of shock fractures in the rock contributed its breakup in the upper atmosphere. Meteorites made available by Chelyabinsk State University researchers were analyzed to learn about the origin of the shock veins and their physical properties. Shock veins are caused by asteroid collisions. When asteroid collide with each other, heat generated by the impact causes iron and nickel components of the objects to melt. These melts cool into thin masses, forming metal veins – shock veins – in the objects.

“One of these meteorites broke along one of these shock veins when we pressed on it during our analysis,” said Derek Sears, a meteoriticist at Ames.

Mike Zolensky, a cosmochemist at NASA’s Johnson Space Center in Houston, may have found why these shock veins (or shock fractures), were so frail. They contained layers of small iron grains just inside the vein, which had precipitated out of the glassy material when it cooled.

“There are cases where impact melt increases a meteorite’s mechanical strength, but Chelyabinsk was weakened by it,” said Zolensky.

The impact that created the shock veins may have occurred as long ago as 4.4 billion years. This would have been 115 million years after the formation of the solar system, according to the research team, who found the meteorites had experienced a significant impact event at that time.

“Events that long ago affected how the Chelyabinsk meteoroid broke up in the atmosphere, influencing the damaging shockwave,” said Jenniskens.

NASA’s Near-Earth Object Program sponsors research to better understand the origin and nature of NEOs. These essential studies are needed to inform our approach to preparing for the potential discovery and deflection of an object on a collision course with the Earth.

NASA’s recently announced asteroid initiative includes the first mission to capture and relocate an asteroid, as well as a grand challenge to find and characterize all asteroid threats to human population. It represents an unprecedented technological feat that will lead to new scientific discoveries and technological capabilities that will help protect our home planet.

Aside from representing a potential threat, the study of asteroids and comets represent a valuable opportunity to learn more about the origins of our solar system, the source of water on the Earth, and even the origin of organic molecules that lead to the development of life.