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Collision Course: A Brief Guide to Earth's Most Interesting Impact Craters

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A Norwegian family arrived at their cabin to open it up for the spring and found a surprise: a large rock had smashed through the roof. It was identified as a 1.3 pound breccia meteorite. It didn't hurt anybody, and its sale price should easily cover the damage to the roof; meteorites are valuable to collectors. But although most meteorites are very small, and to date nobody has been more than bruised by one, some of them are big and make a violent impression where they hit. Here are a few of the more interesting impact craters around:

Barringer Crater, Arizona, USA


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Also known as "Meteor Crater," this was the first crater identified, due to its relatively pristine appearance. It's young, as craters go -- just 50,000 years old -- and it was created by a nickel-iron meteorite about 50 meters across, excavating a crater about 1.2 km across.

Obolon' Crater, Poltava Oblast, Ukraine


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Not all craters are so obvious; sometimes their structure is only apparent in aerial views. Obolon' Crater was detected from the presence of shocked minerals in the surrounding, a tell-tale sign of an impact event. It's 20 km across and is estimated to be about 169 million years old, though there is some evidence it may be quite a bit older. (More on that next.)

Manicouagan Crater, Quebec, Canada


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Visible from space as a ring-shaped lake, this 100 km multi-ringed crater (with a 70 km central ring that is now Manicouagan Reservoir) was created by the impact of a 5km asteroid about 216 million years ago. What's interesting about this crater is that, if you account for plate tectonics and then roll the clock back about 216 million years, this crater has an eerily precise alignment with several other craters: Rochechouart in France, St. Martin in Manitoba, Obolon' in the Ukraine, and Red Wing crater in North Dakota. All of these craters may have been produced by a meteor train, the result of an object breaking up due to tidal forces or collisions.

Gosses Bluff Crater, Northern Territory, Australia


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What's left of this one is only 5 km across, but that's really only the central uplift that is found in some larger craters; the outer rim has mostly eroded away. This crater dates back about 142 million years. The local Aborigines regard it as sacred and, interestingly, give it an origin story hinting at its true origins: their story is that the child of the morning and evening stars fell out of the sky and hit the Earth in this spot; the shape of the bluff is evocative of its origin.

Karakul Crater, Pamir Mountains, Tajikistan



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This relatively young crater (between 5 and 25 million years old) is in Tajikistan and features a large lake at its center. The overall depression is 52 km across.

Sudbury Basin, Ontario, Canada



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This highly elliptical and also frighteningly large impact crater is difficult to see; it is shallow (the blow was a glancing one) and is heavily eroded and largely covered in vegetation. There is a large lake at one end, and the shape of it is crudely visible as human settlement has been mostly in the valley. The impactor would have been about 10-15 km in size, and struck the Earth about 1.849 billion years ago.

Vredefort Crater, Free State Province, South Africa


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Sudbury is big, but it's not the biggest. At 300 km across, Vredefort is the biggest confirmed impact crater on Earth. It's also the second oldest, at a little over 2 billion years of age. This impactor was probably 5-10 km, but traveling on a more direct course than the one that created Sudbury.

Chicxulub Crater, Yucatan, Mexico

This is not the largest crater on Earth, and you cannot see it at all from the surface. But it's one of the most famous, because this is the one widely suspected to have done in the dinosaurs. It's 180 km across, and the impactor is believed to have been at least 10 km across, striking Earth with a force of roughly 96 teratons of TNT. Geologic evidence indicates that the region was completely underwater at the time, and it would have produced a phenomenal tsunami.

[Gravity map created from public data by Milan Studio and released through Wikimedia Commons.]

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Bruce Weaver / Stringer / Getty Images
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Space
NASA Is Posting Hundreds of Retro Flight Research Videos on YouTube
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Bruce Weaver / Stringer / Getty Images

If you’re interested in taking a tour through NASA history, head over to the YouTube page of the Armstrong Flight Research Center, located at Edwards Air Force Base, in southern California. According to Motherboard, the agency is in the middle of posting hundreds of rare aircraft videos dating back to the 1940s.

In an effort to open more of its archives to the public, NASA plans to upload 500 historic films to YouTube over the next few months. More than 300 videos have been published so far, and they range from footage of a D-558 Skystreak jet being assembled in 1947 to a clip of the first test flight of an inflatable-winged plane in 2001. Other highlights include the Space Shuttle Endeavour's final flight over Los Angeles and a controlled crash of a Boeing 720 jet.

The research footage was available to the public prior to the mass upload, but viewers had to go through the Dryden Aircraft Movie Collection on the research center’s website to see them. The current catalogue on YouTube is much easier to browse through, with clear playlist categories like supersonic aircraft and unmanned aerial vehicles. You can get a taste of what to expect from the page in the sample videos below.

[h/t Motherboard]

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U.S. National Archives and Records Administration, Public Domain, Wikimedia Commons
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5 Things You Didn't Know About Sally Ride
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U.S. National Archives and Records Administration, Public Domain, Wikimedia Commons

You know Sally Ride as the first American woman to travel into space. But here are five things you might not know about the astronaut, who passed away five years ago today—on July 23, 2012—at the age of 61.

1. SHE PROVED THERE IS SUCH THING AS A STUPID QUESTION.

When Sally Ride made her first space flight in 1983, she was both the first American woman and the youngest American to make the journey to the final frontier. Both of those distinctions show just how qualified and devoted Ride was to her career, but they also opened her up to a slew of absurd questions from the media.

Journalist Michael Ryan recounted some of the sillier questions that had been posed to Ride in a June 1983 profile for People. Among the highlights:

Q: “Will the flight affect your reproductive organs?”
A: “There’s no evidence of that.”

Q: “Do you weep when things go wrong on the job?”
A: “How come nobody ever asks (a male fellow astronaut) those questions?"

Forget going into space; Ride’s most impressive achievement might have been maintaining her composure in the face of such offensive questions.

2. SHE MIGHT HAVE BEEN A TENNIS PRO.

When Ride was growing up near Los Angeles, she played more than a little tennis, and she was seriously good at it. She was a nationally ranked juniors player, and by the time she turned 18 in 1969, she was ranked 18th in the whole country. Tennis legend Billie Jean King personally encouraged Ride to turn pro, but she went to Swarthmore instead before eventually transferring to Stanford to finish her undergrad work, a master’s, and a PhD in physics.

King didn’t forget about the young tennis prodigy she had encouraged, though. In 1984 an interviewer playfully asked the tennis star who she’d take to the moon with her, to which King replied, “Tom Selleck, my family, and Sally Ride to get us all back.”

3. HOME ECONOMICS WAS NOT HER BEST SUBJECT.

After retiring from space flight, Ride became a vocal advocate for math and science education, particularly for girls. In 2001 she founded Sally Ride Science, a San Diego-based company that creates fun and interesting opportunities for elementary and middle school students to learn about math and science.

Though Ride was an iconic female scientist who earned her doctorate in physics, just like so many other youngsters, she did hit some academic road bumps when she was growing up. In a 2006 interview with USA Today, Ride revealed her weakest subject in school: a seventh-grade home economics class that all girls had to take. As Ride put it, "Can you imagine having to cook and eat tuna casserole at 8 a.m.?"

4. SHE HAD A STRONG TIE TO THE CHALLENGER.

Ride’s two space flights were aboard the doomed shuttle Challenger, and she was eight months deep into her training program for a third flight aboard the shuttle when it tragically exploded in 1986. Ride learned of that disaster at the worst possible time: she was on a plane when the pilot announced the news.

Ride later told AARP the Magazine that when she heard the midflight announcement, she got out her NASA badge and went to the cockpit so she could listen to radio reports about the fallen shuttle. The disaster meant that Ride wouldn’t make it back into space, but the personal toll was tough to swallow, too. Four of the lost members of Challenger’s crew had been in Ride’s astronaut training class.

5. SHE DIDN'T SELL OUT.

A 2003 profile in The New York Times called Ride one of the most famous women on Earth after her two space flights, and it was hard to argue with that statement. Ride could easily have cashed in on the slew of endorsements, movie deals, and ghostwritten book offers that came her way, but she passed on most opportunities to turn a quick buck.

Ride later made a few forays into publishing and endorsements, though. She wrote or co-wrote more than a half-dozen children’s books on scientific themes, including To Space and Back, and in 2009 she appeared in a print ad for Louis Vuitton. Even appearing in an ad wasn’t an effort to pad her bank account, though; the ad featured an Annie Leibovitz photo of Ride with fellow astronauts Buzz Aldrin and Jim Lovell gazing at the moon and stars. According to a spokesperson, all three astronauts donated a “significant portion” of their modeling fees to Al Gore’s Climate Project.

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