3-D perspective map of the Decorah impact feature looking northward. (Credit: USGS/Adam Kiel graphic/Northeast Iowa RC&D).
A monster lurks under northeastern Iowa. That monster is in the form of a giant buried basin, the result of a meteorite impact in central North America over 470 million years ago.
A recent aerial survey conducted by the state of Minnesota Geological Survey and the United States Geological Survey (USGS) confirms the existence of an impact structure long suspected near the eastern edge of the town of Decorah, Iowa. The goal of the 60 day survey was a routine look at possible mineral and water resources in the region, but the confirmation of the crater was an added plus. Continue reading “Giant Ancient Impact Crater Confirmed in Iowa”
Lecturer at Ural Federal University's Institute of Physics and Technology Viktor Grokhovsky with meteorite fragment found during an expedition in the Chelyabinsk region on February 25, 2013. Credit: RIA Novosti / Pavel Lysizin.
Scientists and meteorites hunters have been on a quest to find bits of rock from the asteroid which exploded over the city of Chelyabinsk in Russia on February 15. More than 100 fragments have been found so far that appear to be from the space rock, and now scientists from Russia’s Urals Federal University have discovered the biggest chunk so far, a meteorite fragment weighing more than one kilogram (2.2 lbs).
The asteroid has been estimated to be about 15 meters (50 feet) in diameter when it struck Earth’s atmosphere, traveling several times the speed of sound, and exploded into a fireball, sending a shockwave to the city below, which broke windows and caused other damage to buildings, injuring about 1,500 people.
A hole in Chebarkul Lake made by meteorite debris. Photo by Chebarkul town head Andrey Orlov. Via RT.com
Fragments of the meteorite have been found along a 50 kilometer (30 mile) trail under the meteorite’s flight path. Small meteorites have also been found in an eight-meter (25 feet) wide crater in the region’s Lake Chebarkul, scientists said earlier this week. Viktor Grokhovsky from the Urals University believes there are more to be found, including a possible biggest chunk that he says may lie at the bottom of Lake Chebarkul. It could be up to 60cm in diameter, he estimated.
This video from NASA explains more:
Please note that while many pieces have been found, and if you are looking to buy a chunk of this famous meteorite, you need to approach this with a lot of skepticism. There have been some reports of people trying to sell pieces that they claim to be from the Ural/Russian meteorite, but they likely are not. Be careful and do your research on the seller before you buy.
A polished slice of one of Russian meteorite samples. You can see round grains called chondrules and shock veins lined with melted rock. The meteorite is probably non-uniform. The preliminary analysis showed that the meteorite belongs to chemical type L or LL, petrologic type 5.
A little more than week ago a 7,000 ton, 50-foot (15-meter) wide meteoroid made an unexpected visit over Russia to become the biggest space rock to enter the atmosphere since the Tunguska impact in 1908. While scientists still debate whether it was asteroid or comet that sent a tree-flattening shockwave over the Tunguska River valley, we know exactly what fell last Friday.
Now is a fitting time to get more familiar with these extraterrestrial rocks that drop from out of nowhere.
The Russian meteoroid – the name given an asteroid fragment before it enters the atmosphere – became a brilliant meteor during its passage through the air. If a cosmic rock is big enough to withstand the searing heat and pressure of entry, fragments survive and fall to the ground as meteorites. Most of the meteors or “shooting stars” we see on a clear night are bits of rock the size of apple seeds. When they strike the upper atmosphere at tens of thousands of miles an hour, they vaporize in a flash of light. Case closed. But the one that boomed over the city of Chelyabinsk was big enough to to survive its last trip around the Sun and sprinkle the ground with meteorites.
The two main smoke trails left by the Russian meteor as it passed over the city of Chelyabinsk. Credit: AP Photo/Chelyabinsk.ru
Ah, but the Russian fireball didn’t get off the hook that easy. The overwhelming air pressure at those speeds combined with re-entry temperatures around 3,000 degrees F (1,650 C) shattered the original space rock into many pieces. You can see the dual trails created by two of the larger hunks in the photo above.
Scientists at Urals Federal University in Yekaterinburg examined 53 small meteorite fragments deposited around a hole in ice-covered Chebarkul Lake 48 miles (77 km) west of Chelyabinsk the following day. Chemical analysis revealed the stones contained 10% iron-nickel metal along with other minerals commonly found in stony meteorites. Since then, hundreds of fragments have been dug out of the snow by people in surrounding villages. As specimens continue to be recovered and analyzed, here’s an overview — and a look at what we know — of these space rocks that pay us a visit from time to time.
Bright fireball breaking up over Yellow Springs, Ohio. Credit: John Chumack
How many times has a meteor taken your breath away? A brilliant fireball streaking across the night sky ranks among the most memorable astronomical sights most of us will ever see. Like objects in your side view mirror, meteors appear closer than they really are. And it’s all the more true when they’re exceptionally bright. Studies show however that meteors burn up at least 50 miles (80 km) overhead. If big enough to remain intact and land on the ground, the fragments go completely dark 5-12 miles (8-19 km) high during the “dark flight” phase. A meteor passing overhead would be at the minimum distance of about 50 miles (80 km) from the observer.
Since most sightings are well off toward one direction or another, you have to add your horizontal distance to the meteor’s height to get a true distance. While some meteors are bright enough to trick us into thinking they landed just over the next hill, nearly all are many miles away. Even the Russian meteor, which put on a grand show and blasted the city of Chelyabinsk with a powerful shock wave, dropped fragments dozens of miles to the west. We lack the context to appreciate meteor distances, perhaps unconsciously comparing what we see to an aerial fireworks display.
Very cute Youtube video of Sasha Zarezina, 8, who lives in a small Siberian village, as she hunts for meteorite fragments in the snow after Friday’s meteor over Russia. Credit: Ben Solomon/New York Times
An estimated 1,000 tons (907 metric tons) to more than 10,000 tons (9,070 MT) of material from outer space lands on Earth every day delivered free of charge from the main Asteroid Belt. Crack-ups between asteroids in the distant past are nudged by Jupiter into orbits that cross that of Earth’s. Most of the stuff rains down as micrometeoroids, bits of grit so small they’re barely touched by heating as they gently waft their way to the ground. Many larger pieces – genuine meteorites – make it to Earth but are missed by human eyes because they fall in remote mountains, deserts and oceans. Since over 70% of Earth’s surface’s is water, think of all the space rocks that must sink out of sight forever.
A fragment of the Sikhote-Alin iron meteorite that fell over eastern Russia (then the Soviet Union) on Feb. 12, 1947. Credit: Bob King
About 6-8 times a year however, a meteorite-producing fireball streaks over a populated area of the world. Using eyewitness reports of time, direction of travel along with more modern tools like video surveillance cameras and Doppler weather radar, which can ping the tracks of falling meteorites, scientists and meteorite hunters have a great many clues on where to look for space rocks.
Since most meteorites break into pieces in mid-air, the fragments are dispersed over the ground in a large oval called the strewnfield. The little pieces fall first and land at the near end of the oval; the bigger chunks travel farthest and fall at the opposite end.
When a new potential meteorite falls, scientists are eager to get a hold of pieces as soon as possible. Back in the lab, they measure short-lived elements called radionuclides created when high-energy cosmic rays in space alter elements in the rock. Once the rock lands on Earth, creation of these altered elements stops. The proportions of radionuclides tell us how long the rock traveled through space after it was ejected by impact from its mother asteroid. If a meteorite could write a journal, this would be it.
Other tests that examine the decay of radioactive elements like uranium into lead tells us the age of the meteorite. Most are 4.57 billion years old. Hold a meteorite and you’ll be whisked back to a time before the planets even existed. Imagine no Earth, no Jupiter.
10x closeup of a very thin slice through a chondrule in the meteorite NWA 4560. Crystals of olivine (bright colors) and pyroxene (grays) are visible. Credit: Bob King
Many meteorites are jam-packed with tiny rocky spheres called chondrules. While their origin is still a topic of debate, chondrules (KON-drools) likely formed when blots of dust in the solar nebula were flash-heated by the young sun or perhaps by powerful bolts of static electricity. Sudden heating melted the motes into chondrules which quickly solidified. Later, chondrules agglomerated into larger bodies that ultimately grew into planets through mutual gravitational attraction. You can always count on gravity to get the job done. Oh, just so you know, meteorites are no more radioactive than many common Earth rocks. Both contain trace amounts of radioactive elements at trifling levels.
A stunning slice of the Glorieta pallasite meteorite cut thin enough to allow light to shine through its many olivine crystals. Click to see more of Mike’s photos. Credit: Mike Miller
Meteorites fall into three broad categories – irons (mostly metallic iron with smaller amounts of nickel), stones (composed of rocky silicates like olivine, pyroxene and plagioclase and iron-nickel metal in form of tiny flakes) and stony-irons (a mix of iron-nickel metal and silicates). The stony-irons are broadly subdivided into mesosiderites, chunky mixes of metal and rock, and pallasites.
Pallasites are the beauty queens of the meteorite world. They contain a mix of pure olivine crystals, better known as the semi-precious gemstone peridot, in a matrix of iron-nickel metal. Sliced and polished to a gleaming finish, a pallasite wouldn’t look out of place dangling from the neck of an Oscar winner. About 95% of all found or seen-to-fall meteorites are the stony variety, 4.4% are irons and 1% stony-irons.
A slice of the NWA 5205 meteorite from the Sahara Desert displays wall-to-wall chondrules. Credit: Bob King
Earth’s atmosphere is no friend to space rocks. Collecting them early prevents damage by the two things most responsible for keeping us alive: water and oxygen. Unless a meteorite lands in a dry desert environment like the Sahara or the “cold desert” of Antarctica, most are easy prey to the elements. I’ve seen meteorites collected and sliced open within a week after a fall that already show brown stains from rusting nickel-iron. Antarctica is off-limits to all but professional scientists, but thanks to amateur collectors’ efforts in the Sahara Desert, Oman and other regions, thousands of meteorites including some of the rarest types, have come to light in recent years.
Greg Hupe, renowned meteorite hunter, wears a big smile after finding a fresh 33.7g meteorite of the Mifflin, Wis. fall in 2010. Credit: Greg Hupe
Hunters share their finds with museums, universities and through outreach efforts in the schools. A portion of the material is sold to other collectors to finance future expeditions, pay for plane tickets and sit down to a good meal after the hunt. Finding a meteorite of your own is hard but rewarding work. If you’d like to have a go at it, here’s a basic checklist of qualities that separate space rocks from Earth rocks:
* Attracts a magnet. Most meteorites – even stony ones – contain iron.
* Most are covered with a matt-black, slightly bumpy fusion crust that colors dark brown with age. Look for hints of rounded chondrules or tiny bits of metal sticking up through the crust.
* Aerodynamic shape from its flight through the atmosphere, but be wary of stream-eroded rocks which appear superficially similar
* Some are dimpled with small thumbprint-like depressions called regmaglypts. These form when softer materials melt and stream away during atmospheric entry. Some meteorites also display hairline-thin, melted-rock flow lines rippling across their exteriors.
Beware of imitations! These are chunks of industrial slag that are often confused with real meteorites. Meteorites don’t have bubbly surfaces. Credit: Bob King
Should your rock passes the above tests, file off an edge and look inside. If the interior is pale with shining flecks of pure metal (not mineral crystals), your chances are looking better. But the only way to be certain of your find is to send off a piece to a meteorite expert or lab that does meteorite analysis. Industrial slag with its bubbly crust and dark, smooth volcanic rocks called basalts are the most commonly found meteor-wrongs. We imagine that meteorites must have bubbly crust like a cheese pizza; after all, they’ve been oven-baked by the atmosphere, right? Nope. Heating only happens in the outer millimeter or two and crusts are generally quite smooth.
Look Ma, no chondrules. NWA 3147 is an achondrite eucrite meteorite that probably originated from the asteroid Vesta. Credit: Bob King
Stony meteorites are further subdivided into two broad types – chondrites, like the Russian fall, and achondrites, so-called because they lack chondrules. Achondrites are igneous rocks formed from magma deep within an asteroid’s crust and lava flows on the surface. Some eucrites (YOU-crites), the most common type of achondrite, likely originated as fragments shot into space from impacts on Vesta. Measurements by NASA’s Dawn space mission, which orbited the asteroid from July 2011 to September 2012, have found great similarities between parts of Vesta’s crust and eucrites found on Earth.
We also have meteorites from Mars and the Moon. They got here the same way the rest of them did; long-ago impacts excavated crustal rocks and sent them flying into space. Since we’ve studied moon rocks brought back by the Apollo missions and sampled Mars atmosphere with a variety of landers, we can compare minerals and gases found inside potential moon and Mars meteorites to confirm their identity.
Some of the 53 chondrite meteorites found around Chebarkul Lake. Many are coated with a thin crust of melted and blackened rock heating by the atmosphere. The sign reads: Meteorite Chebarkul. Credit: AP / The Urals Federal University Press Service, Alexander Khlopotov
Scientists study space rocks for clues of the Solar System’s origin and evolution. For the many of us, they provide a refreshing “big picture” perspective on our place in the Universe. I love to watch eyes light up with I pass around meteorites in my community education astronomy classes. Meteorites are one of the few ways students can “touch” outer space and feel the awesome span of time that separates the origin of the Solar System and present day life.
'Name That Space Rock' -- describes the difference between those flying rocks from space. Credit and copyright: Tim Lilis. Used by permission.
With all the various space rocks flying by and into Earth last Friday, perhaps you’ve been wondering about the correct terminology, since a rock from space has different names depending on what it is made of and where it is.
Infographics artist Tim Lillis has put together a primer of sorts, in the form of an infographic, describing the different between a comet, asteroid, meteoroid, meteor and meteorite.
Asteroids are generally larger chunks of rock that come from the asteroid belt located between the orbits of Mars and Jupiter. Sometimes their orbits get perturbed or altered and some asteroids end up coming closer to the Sun, and therefore closer to Earth.
Comets are much like asteroids, but might have a more ice, methane, ammonia, and other compounds that develop a fuzzy, cloud-like shell called a coma – as well as a tail — when it gets closer to the Sun. Comets are thought to originate from two different sources: Long-period comets (those which take more than 200 years to complete an orbit around the Sun) originate from the Oort Cloud. Short-period comets (those which take less than 200 years to complete an orbit around the Sun) originate from the Kuiper Belt.
Space debris smaller than an asteroid are called meteoroids. A meteoroid is a piece of interplanetary matter that is smaller than a kilometer and frequently only millimeters in size. Most meteoroids that enter the Earth’s atmosphere are so small that they vaporize completely and never reach the planet’s surface. And when they do enter Earth’s atmosphere, they gain a different name:
Meteors. Another name commonly used for a meteor is a shooting star. A meteor is the flash of light that we see in the night sky when a small chunk of interplanetary debris burns up as it passes through our atmosphere. “Meteor” refers to the flash of light caused by the debris, not the debris itself.
If any part of a meteoroid survives the fall through the atmosphere and lands on Earth, it is called a meteorite. Although the vast majority of meteorites are very small, their size can range from about a fraction of a gram (the size of a pebble) to 100 kilograms (220 lbs) or more (the size of a huge, life-destroying boulder).
Thanks again to Tim Lillis for sharing his infographic with Universe Today. For more info about Tim’s work, see his Behance page, Flickr site, Twitter, or his website.
Meteorites from Mars, like NWA 7034 (shown here), contain evidence of Mars' watery past. Credit: NASA
Martian meteorite NWA 7034 weighs approximately 320 grams (11 ounces). Credit: NASA
A 2-billion-year-old rock found in the Sahara desert has been identified as a meteorite from Mars’ crust, and it contains ten times more water than any other Martian meteorite found on Earth. It also contains organic carbon. The age of the rock, called NWA 7034, would put its origins in the early era of the most recent geologic epoch on Mars, the Amazonian epoch. While its composition is different from any previously studied Martian meteorite, NASA says it matches surface rocks and outcrops that have been studied by Mars rovers and Mars-orbiting satellites.
“The contents of this meteorite may challenge many long held notions about Martian geology,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “These findings also present an important reference frame for the Curiosity rover as it searches for reduced organics in the minerals exposed in the bedrock of Gale Crater.”
This new class of meteorite was found in 2011 in the Sahara Desert. Designated Northwest Africa (NWA) 7034, and nicknamed “Black Beauty,” it weighs approximately 320 grams (11 ounces). Research teams from the University of New Mexico, the University of California at San Diego and the Carnegie Institution in Washington analyzed mineral and chemical composition, age, and water content.
NWA 7034 is made of cemented fragments of basalt, rock that forms from rapidly cooled lava. The fragments are primarily feldspar and pyroxene, most likely from volcanic activity.
“This Martian meteorite has everything in its composition that you’d want in order to further our understanding of the Red Planet,” said Carl Agee, leader of the analysis team and director and curator at the University of New Mexico’s Institute of Meteoritics in Albuquerque. “This unique meteorite tells us what volcanism was like on Mars 2 billion years ago. It also gives us a glimpse of ancient surface and environmental conditions on Mars that no other meteorite has ever offered.”
There are about one hundred Martian meteorites that have been collected on Earth. They were all likely blasted off the Red Planet by either an asteroid or comet impact, and then spent millions of years traveling through space before falling to Earth.
Researchers theorize the large amount of water contained in NWA 7034 may have originated from interaction of the rocks with water present in Mars’ crust. The meteorite also has a different mixture of oxygen isotopes than has been found in other Martian meteorites, which could have resulted from interaction with the Martian atmosphere.
Scientists say the age of NWA 7034 is important because it is much older than most other Martian meteorites.
“We now have insight into a piece of Mars’ history at a critical time in its evolution,” said Mitch Schulte, program scientist for the Mars Exploration Program at NASA Headquarters.
Most Martian meteorites are divided into three rock types, named after three meteorites; Shergotty, Nakhla, and Chassigny. These “SNC” meteorites currently number about 110. Their point of origin on Mars is not known and recent data from lander and orbiter missions suggest they are a mismatch for the Martian crust. Although NWA 7034 has similarities to the SNC meteorites, including the presence of macromolecular organic carbon, this new meteorite has many unique characteristics.
“The texture of the NWA meteorite is not like any of the SNC meteorites,” said co-author Andrew Steele, who led the carbon analysis at the Carnegie Institution’s Geophysical Laboratory. “This is an exciting measurement in Mars and planetary science. We now have more context than ever before to understanding where they may come from.”
Credit: Pierre Martin of Arnprior, Ontario, Canada.
A dazzling daytime fireball zipped across New Mexico and Colorado yesterday creating a stir among law enforcement agencies, news organizations, radio stations and briefly grounded air tankers fighting wildfires west of Colorado Springs.
According to the Denver Post, Pueblo air-dispatch received reports of “balls of fire or something in the air.” As a precaution, officials grounded flights to ensure no aircraft were hit. Flights resumed 90 minutes later.
The event occurred between 12:35 and 12:40 MDT Wednesday afternoon. Witnesses say the fireball lasted about 3 seconds about 45 degrees above the ground, heading from the north to the south and ending near the horizon, with a tail color ranging from bright white to yellow and red. Some of the nearly 20 reports received by the American Meteor Society report that the brightness of the fireball was brighter than a full moon; some reporting it brighter than the Sun.
A fireball is a meteor that is larger and brighter than normal. Although typically visible after sunset, dramatic fireballs have been recorded during the daytime, such as the April 22, 2012 bright daytime meteor that was seen over California in the US. Usually meteors are smaller than a pebble and move very fast. As the object encounters increased friction from the air in the upper atmosphere, it begins to get hot and glow. Most meteors burn up before hitting the ground. But some survive to be picked up and put in museums. Scientists estimate that nearly 100 tons of space dust lands on Earth every day. Most of it lands in the ocean.
The North American Aerospace Defense Command (NORAD) based at Peterson Air Force Base near Colorado Springs told the Denver Post they were not tracking any man-made objects in the area.
The Denver Museum of Nature and Science has meteor cameras stationed around the state. Unfortunately, they are turned off during the day and no video or pictures have surfaced.
Astronomers and meteor/meteorite enthusiasts will certainly be interested in seeing any pictures or videos of the event, and so are we! If saw the event, or happened to capture it on a camera or surveillance video, you can send it to us or post it on our Flickr page.
Lead image caption: A Perseid fireball meteor. Credit: Pierre Martin of Arnprior, Ontario, Canada.
Editor’s note: This guest post was written by Andy Tomaswick, an electrical engineer who follows space science and technology.
The search for biologically created organic molecules on Mars goes back at least to the 1970s with the Viking program. Those missions had famously mixed results, and so the search for carbon-based life on Mars continues to this day. Researchers keeping piling on more and more evidence to excite astrobiologists and new results published in a study by the Planetary Science Institute and the Carnegie Institute of Washington may heighten their enthusiasm.
The latest results come from a team led by Andrew Steele of the Carnegie Institution for Science who surveyed meteorites from Mars, which covered a 4.2 billion year time span of Martian geology. While it is no surprise that there are organics on Mars — that Martian meteorites contain carbon-based molecules has been known for years — the team confirmed those findings by detecting organics on ten of the eleven meteorites they examined. However, questions remained as to where exactly the meteorite-bound organic molecules came from and, if they were from Mars, what had created them?
The team set out to answer these questions and came to the conclusion that the molecules are indeed from Mars and not the result of some cross-contamination from Earth’s biosphere. However, they also found that the molecules were not created by any biological process. The organics actually formed in the chunks of rock that later became the meteorites that transported them to earth. Their formation was part of a volcanic process that traps carbon in crystal structures formed by cooling magma. Through a series of non-biological chemical reactions, the complex organics found in the meteorites are created using the carbon trapped in these crystals.
The team also casts doubt on another possible explanation: whether the organics might be caused by emissions from microbes that had migrated into the volcano via tectonic processes similar to those on Earth. They point out that Mars does not have the tectonic activity similar to Earth so there is very little likelihood that the molecules are created by microbial activity.
That might sound like a depressing result for the astrobiologists. But the important finding from this study is that Mars has been natively and naturally creating complex organic molecules for 4.2 billion years and may be still be doing so today. Since the creation of organic molecules on Earth was a precursor to life, scientists can still hold out hope that the same life-creating process might have already happened on the red planet.
Interestingly, one of the Martian meteorites that was studied was the famous ALH84001, the meteorite that some researchers claimed in 1996 might contain fossils from Mars. That claim was subsequently strongly challenged, and studies of the rock are ongoing. ALH84001 is a portion of a meteorite that was dislodged from Mars by a huge impact about 16 million years ago and that fell to Earth in Antarctica approximately 13,000 years ago. The meteorite was found in Allan Hills ice field in Antarctica.
Lead image caption: ALH84001 is one of 10 rocks from Mars in which researchers have found organic carbon compounds that originated on Mars without involvement of life. Credit: NASA/JSC/Stanford University
Dr. Peter Jenniskens take a closer look at the image from the AVS Cineflex HiDEF camera mounted on the nose of the Eureka Airship. Mike Coop, can be seen in the background checking the map, further back other flight members continue to look for potential impact sites. Image credit: NASA / Eric James
Video footage has finally surfaced of the daytime fireball that illuminated the sky over the Sierra Nevada Mountains in California back in April. NASA and the SETI Institute had asked the public to submit any amateur photos or video footage of the event, and previously a just few photos were taken of the event, even though it happened in broad daylight and created sonic booms that were heard over a wide area, back on Sunday, April 22, 2012 at 7:51 a.m. PDT. A few weeks later, Shon Bollock, who was making a time-lapse kayaking video just outside Kernville, California realized he had captured the bolide streaking through the air. This video shows the event several times, successively zooming in for a closer look. According to NASA it is the only footage of the meteor thus far.
Meteorite hunters have been successful in locating fragments of the meteor, now called the Sutter’s Mill meteor since the event occurred near the area famous for where gold was discovered back in 1848, creating the California gold rush.
NASA estimated fragments could be dispersed over a 16-km (10-mile) area.
Phil Plait says the video is being studied by astronomers and meteoriticists to try to calculate the trajectory, speed, and possible orbit of the object, which is difficult with just one video, so if anyone finds they have ‘accidently’ taken footage of the event, contact the NASA Lunar Science Institute at the NASA Ames Research Center.
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NASA used an airship to search for meteorites from this event. Noted meteorite expert Peter Jenniskens said the meteorites found so far from the fall are Carbonaceous Chondrites from the CM group of meteorites, “a rare type of primitive meteorite rich in organic compounds,”and scientists have precious few samples of this kind of material. The meteorites are very interesting to scientists from an astrobiology perspective, as they contain molecules related to how the building blocks for life on Earth may have been delivered from outer space. Scientist believe that this meteor could hold the answers to the origin of life on Earth and the universe. By studying the meteor, scientists also will learn more about the early solar system and the formation of our planets.
“This is among the most chemically primitive meteorites,” said NLSI Deputy Director Greg Schmidt. “It’s like asking ‘how did life on Earth begin?’ and then having a fossil fall right in your back yard. This is exciting stuff — who knows what’s inside? The Sutter’s Mill Meteorite could be the most profound sample collected in over 40 years.”
A Murchison meteorite specimen at the National Museum of Natural History in Washington DC.
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Where does the methane on Mars come from? That has been one of the biggest unanswered questions in planetary science since the discovery of large plumes of methane gas in the Martian atmosphere. Scientists have been trying to figure out how the planet’s environment or geology can keep replenishing this short-lived gas, and of course, in the back of everyone’s mind is whether the methane has any connection to possible life on Mars.
A new potential explanation squelches both the life and environment prospect and offers a unique answer. A group of researchers found that meteorites, which continually bombard the surface of Mars, may contain enough carbon compounds to generate methane when they are exposed to strong UV sunlight.
“Whether or not Mars is able to sustain life is not yet known, but future studies should take into account the role of sunlight and debris from meteorites in shaping the planet’s atmosphere,” said Dr. Andrew McLeod, of the University of Edinburgh, co-author of a new study published in Nature this week.
The group of European researchers looked at the famous Murchison meteorite, a carbonaceous chondrite meteorites that fell in Australia more than 40 years ago. Carbonaceous chondrites are very common meteorites, so they likely will be falling on Mars. The team exposed particles of the Murchison meteorite to levels of ultraviolet radiation equivalent to sunlight on Mars.
When the meteorite pieces were exposed to ample amounts of UV light the meteor fragments rapidly released methane. After the UV exposure was reduced, the amount of methane produced would lessen, but if there were other activities, such as heating, shaking or lowering the pressure on the meteorite, the amount of methane released would rise again.
With Mars thin atmosphere, UV light easily gets to the surface of the planet. The thin atmosphere also allows more meteorites to hit Mars than on Earth (estimates range from just a few thousands of metric tons to as much as 60,000 metric tons.) The team said that temperature changes on Mars, especially during the summertime when it gets warm, could account for a boost of methane release from meteorites, and seasonal dust storms could shake or move the meteorites.
However, while only small amounts of methane are present in the Martian atmosphere, it seems to be coming from very specific, localized sources. Meteorites would likely be falling across the planet.
Top: Map of methane concentrations in Autumn (first martian year observed). Peak emissions fall over Tharsis (home to the Solar System's largest volcano, Olympus Mons), the Arabia Terrae plains and the Elysium region, also the site of volcanos. Bottom: True colour map of Mars. Credit: NASA/Università del Salento
Additionally, levels of methane vary in the seasons, and are highest in autumn in the northern hemisphere, with localized peaks of 70 parts per billion. There is a sharp decrease in winter, with only a faint band of methane appearing in the atmosphere between 40-50 degrees north.
Methane was first detected in the Martian atmosphere by ground based telescopes in 2003 and confirmed a year later by ESA’s Mars Express spacecraft. In 2009, observations using ground based telescopes showed the first evidence of a seasonal cycle.
Other research has said that the methane in the Martian atmosphere lasts less than a year, making it a flitting – and difficult – feature to study.
Another issue is that the estimates for the amount of meteorites hitting Mars’ surface would likely not bring enough carbon to explain the amount of methane seen in the atmosphere.
The researchers said, however, that their findings give valuable insights into the planet’s atmosphere and these findings would be helpful for future robotic missions to Mars so scientists could fine-tune their experiments, potentially making their trips more valuable.
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.
