The cross section area of the particle collected from the asteroid Itokawa using Hayabusa spacecraft. Credit: Osaka University
Within Earth’s orbit, there are an estimated eighteen-thousands Near-Earth Asteroids (NEAs), objects whose orbit periodically takes them close to Earth. Because these asteroids sometimes make close flybys to Earth – and have collided with Earth in the past – they are naturally seen as a potential hazard. For this reason, scientists are dedicated to tracking NEAs, as well as studying their origin and evolution.
DeeDee and Frank Hommel pose with the 760 pound (345 kilogram) Clarendon (c) meteorite discovered on their land. The stony meteorite may be the second largest single chondrite ever found in the United States. It displays dark fusion crust on the topside; the bottom side, which faced down in the soil, is covered with caliche (ka-LEE-chee), a cement-like mineral deposit of calcium carbonate. Credit: Ruben Garcia
On April 6, 2015, Frank Hommel was leading a group of guests at his Bar H Working Dude Ranch on a horseback ride. The horses got thirsty, so Hommel and crew rode cross-country in search of a watering hole. Along the way, his horse Samson suddenly stopped and refused to go any further. Ahead of them was a rock sticking out of the sandy soil. Hommel had never seen his horse act this way before, so he dismounted to get a closer look at the red, dimpled mass. Something inside told him this strange, out of place boulder had to be a meteorite.
This photo was taken of the Clarendon (c) meteorite before it was removed from the ground. There appear to be several broken fragments at lower and center left. The meteorite is a chondrite, composed of rock found in the crust of asteroids. Credit: Frank and DeeDee Hommel
Here’s the crazy thing — Hommel’s hunch was correct. Lots of people pick up an odd rock now and then they think might be a meteorite, but in nearly every case it isn’t. Meteorites are exceedingly rare, so you’re chances of happening across one are remote. But this time horse and man got it right.
The rock that stopped Samson that April day was the real deal and would soon be classified and named the Clarendon (c) stony meteorite. Only the top third of the mass broke the surface; there was a lot more beneath the soil. Hommel used a tractor to free the beast and tow it to his home. Later, when he and his wife DeeDee got it weighed on the feed store scale, the rock registered a whopping 760 pounds (345 kilograms). Hommel with others returned to the site and recovered an additional 70 pounds (32 kilograms) of loose fragments scattered about the area.
This view of the 760-pound meteorite shows relatively fresh fusion crust from melting of the outer millimeter or two of the meteoroid during its heated passage through Earth’s atmosphere. You can also see lots of thumbprints or regmaglypts (left side), which form when softer materials in the rock are ablated away by brief but intense heat and pressure experienced during the fall. Credit: Ruben Garcia
At this point, Frank and DeeDee couldn’t be certain it was a meteorite. Yes, it attracted a magnet, a good sign, but the attraction was weak. Frank had his doubts. To prove one way or another whether this rusty boulder came from space or belonged to the Earth, DeeDee sent a photo of it to Eric Twelker of Juneau, Alaska, a meteorite seller who maintains the Meteorite Market website.Twelker thought it looked promising and wrote back saying so. Six months later, the family sent him a sample which he arranged to have tested by Dr. Tony Irving at the University of Washington.
The Bar H Dude Ranch run by DeeDee and Frank Hommel, finders of the Clarendon (c) meteorite. Credit: Ruben Garcia
Irving’s analysis revealed bright grains of iron-nickel metal and an abundance of chondrules, round grains composed of minerals that were flash-heated into a “fiery rain” in the solar nebula 4.5 billion years ago. When they cooled, the melted material congealed into small solid spheres several millimeters across that were later incorporated into the planetary embryos that grew into today’s planets and asteroids. Finding iron-nickel and chondrules proved beyond a shadow that the Hommels’ rock was a genuine stone from space.
In an e-mail communication, Twelker recounted his part of the story:
“I get about six to a dozen inquiries on rocks every day. I try to answer all of them — and give a rock ID if possible. I have to say my patience gets tried sometimes after looking at slag, basalt, and limestone day after day. But if I am in the right mood, then it is fun. This one made it fun. Over the years, I’ve probably had a half dozen discoveries this way, but this is by far the most exciting.”
This small slice of Northwest Africa 2793, an L4 chondrite, is similar to Clarendon (c). Flecks of iron-nickel metal give the cut surface a sparkly appearance. Several round chondrules are visible, especially near the bottom edge. Credit: Bob King
Irving pigeonholed it as an L4 chondrite meteorite. L stands for low-iron and chondrite indicates it still retains its ancient texture of chondrules that have been little altered since their formation. No one knows how long the meteorite has sat there, but the weathering of its surface would seem to indicate for a long time. That said, Hommel had been this way before and never noticed the rock. It’s possible that wind gradually removed the loosely-bound upper soil layer — a process called deflation — gradually exposing the meteorite to view over time.
Once a meteorite has been analyzed and classification, the information is published in the Meteorite Bulletin along with a chemical analysis and circumstances of its discovery. Meteorites are typically named after the nearest town or prominent geographical feature where they’re discovered or seen to fall. Because it was found on the outskirts of Clarendon, Texas, the Hommels’ meteorite took the town’s name. The little “c” in parentheses after the name indicates it’s the third unique meteorite found in the Clarendon area. Clarendon (b) turned up in 1981 and Clarendon (a) in 1979. Both are H5 (high metal) unrelated stony chondrites.
Ruben Garcia, a.k.a. Mr. Meteorite, arranged the sale of the Clarendon (c) meteorite to Texas Christian University. Courtesy of Ruben Garcia
When Clarendon (c) showed up in the Bulletin late last month, meteorite hunter, dealer and collector Ruben Garcia, better known as Mr. Meteorite, quickly got wind of it. Garcia lives in Phoenix and since 1998 has made his livelihood buying and selling meteorites. He got into the business by first asking himself what would be the funnest thing he could do with his time. The answer was obvious: hunt meteorites!
These rusty rocks, chips off asteroids, have magical powers. Ask any meteorite collector. Touch one and you’ll be transported to a time before life was even a twinkle in evolution’s eye. Their ancientness holds clues to that deepest of questions — how did we get here? Scientists zap them with ion beams, cut them into translucent slices to study under the microscope and even dissolve them in acid in search of clues for how the planets formed.
Garcia contacted the Hommels and posed a simple question:
“Hey, you have a big meteorite on your property. Do you want to sell it?”
They did. So Mr. Meteorite put the word out and two days later Texas Christian University made an offer to buy it. After a price was agreed upon, Garcia began making plans to return to Clarendon soon, load up the massive missive from the asteroid belt on his trailer and truck it to the university where the new owner plans to put it on public display, a centerpiece for all to admire.
Visit the largest chondrite ever found in Texas
“How amazing to walk into a dude ranch and see a museum quality specimen,” said Garcia on his first impression of the stone. “I’ve never seen a meteorite this big outside of a museum or gem show.” Ruben joined Frank to collect a few additional fragments which he plans to put up for sale sometime soon.
So how does Clarendon (c) rank weigh-wise to other meteorite falls and finds? Digging through my hallowed copy of Monica Grady’s Catalogue of Meteorites, it’s clear that iron meteorites take the cake for record weights among all meteorites.
A singe chondrule in a thin section of the meteorite NWA 4560 is seen through a polarizing microscope at a magnification of 10x. Crystals of olivine (bright colors) and pyroxene (darker) are visible. Astronomers believe chondrules were among the first solid material to form in the early solar system when some form of flash heating melted nebular dust. The dust congealed into tiny spheres that were later incorporated into planetesimals and ultimately the planets. Credit: Bob King
But when it comes to stony chondrites, Clarendon (c) is by far the largest individual space rock to come out of Texas. It also appears to be the second largest individual chondrite meteorite ever found in the United States. Only the Paragould meteorite, which exploded over Arkansas in 1930, dropped a larger individual — 820 pounds (371.9 kg) of pure meteorite goodness that’s on display at the Arkansas Center for Space and Planetary Sciences in Fayetteville. There’s truth to the saying that everything’s bigger in Texas.
Every meteorite has a story. Some are witnessed falls, while others fall unnoticed only to be discovered decades or centuries later. The Clarendon meteorite parent body spent billions of years in the asteroid belt before an impact broke off a fragment that millions of years later found its way to Earth. Did this chip off the old block bury itself in Texas soil 100 years ago, a thousand? No one can say for sure yet. But one April afternoon in 2015 they stopped a man and his horse dead in their tracks.
*** If you’d like tips on starting your own meteorite collection, check out my new book, Night Sky with the Naked Eye. It covers all the wonderful things you can see in the night sky without special equipment plus additional topics including meteorites. The book publishes on Nov. 8, but you can pre-order it right now at these online stores. Just click an icon to go to the site of your choice — Amazon, Barnes & Noble or Indiebound. It’s currently available at the first two outlets for a very nice discount:
Apollo 16 astronaut Charlie Duke collects lunar samples during EVA on April 23, 1972 (NASA)
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New investigations of lunar samples collected during the Apollo missions have revealed origins from beyond the Earth-Moon system, supporting a hypothesis of ancient cataclysmic bombardment for both worlds.
Samples of Apollo 16 breccia that contain chondritic material (JSC)
Using scanning electron microscopes, researchers at the Lunar-Planetary Institute and Johnson Space Center have re-examined breccia regolith samples returned from the Moon, chemically mapping the lunar rocks to discern more compositional detail than ever before.
What they discovered was that many of the rocks contain bits of material that is chondritic in origin — that is, it came from asteroids, and not from elsewhere on the Moon or Earth.
Chondrites are meteorites that originate from the oldest asteroids, formed during the development of the Solar System. They are composed of the initial material that made up the stellar disk, compressed into spherical chondrules. Chondrites are some of the rarest types of meteorites found on Earth today but it’s thought that at one time they rained down onto our planet… as well as our moon.
The Lunar Cataclysm Hypothesis suggests that there was a period of extremely active bombardment of the Moon’s surface by meteorite impacts around 3.9 billion years ago. Because very few large impact events — based on melt rock samples — seem to have taken place more than 3.85 billion years ago, scientists suspect such an event heated the Moon’s surface enough prior to that period to eradicate any older impact features — a literal resurfacing of the young Moon.
There’s also evidence that there was a common source for the impactors, based on composition of the chondrites. What event took place in the Solar System that sent so much material hurtling our way? Was there a massive collision between asteroids? Did a slew of comets come streaking into the inner solar system? Were we paid a brief, gravitationally-disruptive visit by some other rogue interstellar object? Whatever it was that occurred, it changed the face of our Moon forever.
Curiously enough, it was at just about that time that we find the first fossil evidence of life on Earth. If there’s indeed a correlation, then whatever happened to wipe out the Moon’s oldest craters may also have cleared the slate for life here — either by removing any initial biological development that may have occurred or by delivering organic materials necessary for life in large amounts… or perhaps a combination of both.
Timeline for the Lunar Cataclysm Hypothesis (LPI)
The new findings from the Apollo samples provide unambiguous evidence that a large-scale impact event was taking place during this period on the Moon — and most likely on Earth too. Since the Moon lacks atmospheric weathering or water erosion processes it serves as a sort of “time capsule”, recording the evidence of cosmic events that take place around the Earth-Moon neighborhood. While evidence for any such impacts would have long been erased from Earth’s surface, on the Moon it’s just a matter of locating it.
In fact, due to the difference in surface area, Earth may have received up to ten times more impacts than the Moon during such a cosmic cataclysm. With over 1,700 craters over 20 km identified on the Moon dating to a period around 3.9 billion years ago, Earth should have 17,000 craters over 20 km… with some ranging over 1,000 km! Of course, that’s if the craters could had survived 3.9 billion years of erosion and tectonic activity, which they didn’t. Still, it would have been a major event for our planet and anything that may have managed to start eking out an existence on it. We might never know if life had gained a foothold on Earth prior to such a cataclysmic bombardment, but thanks to the Moon (and the Apollo missions!) we do have some evidence of the events that took place.
Sample of lunar impact melt breccia, showing exterior and chondrule-filled interior. (Click for sample report.) Source: JSC
The LPI-JSC team’s paper was submitted to the journal Science and accepted for publication on May 2. See the abstract here, and read more on the Lunar Science Institute’s website here.
And if you want to browse through the Apollo lunar samples you can do so in depth on the JSC Lunar Sample Compendum site.
