It Came From Space! Man-Made Objects That Crashed Back to Earth

Most orbital debris is in low Earth orbit, where "what goes up must come down" — derelict satellites, spent rocket boosters, explosive bolt shrapnel, payload fairings, interstage structures, payload adapters, spin-up counterweights, and more. Most reentering debris is small and burns up on reentry. But some of it is large and survives reentry. Occasionally, people even find it. To date, no one is known to have been injured, and, statistically speaking, debris is most likely to fall over water. But it's really only a matter of time before someone does get hurt.

Here is a look at some of the more interesting man-made objects that have fallen from space.

Cosmos 954

The Soviet Union fielded an assortment of radar ocean reconnaissance spacecraft (RORSATs) powered not by solar arrays but by actual honest-to-gosh nuclear reactors. They were designed to eject their nuclear cores to a high, disposal orbit at the end of their lifetimes, but on at least one occasion, this did not happen. Cosmos 954's core was still on board when it reentered the atmosphere on January 24, 1978. Although another RORSAT with a similar predicament had wound up safely in the ocean, this one wasn't so lucky; highly radioactive debris was scattered across the Northwest Territories, Alberta, and Saskatchewan, Canada, on a 600 km path. The Soviets refused to acknowledge that any material had survived reentry until a joint US/Canadian recovery mission cleaned up the debris and billed the USSR more than six million Canadian dollars. (The USSR ultimately paid about half of that.) Most of the spacecraft's mass remained unaccounted for, however. This is a bit concerning since, of the 1% of fuel that was recovered, one fragment was so radioactive that a person holding it for a moment would receive a lethal dose.

Members of Operation Morning Light, wearing snowshoes and winter survival gear, use Geiger counters to locate debris.


The most famous piece of space debris ever, this 69,000 kg space station had been built from an unused S-IVB upper stage from a Saturn V, and boosted into orbit by another Saturn V. Today, it holds the record for the third largest space station after the ISS and Mir. After consuming most of the remaining Apollo hardware, the station was abandoned, with the plan of sending the new Space Shuttle up to reboost it and periodically visit. The Sun had other ideas; solar activity puffed out the Earth's atmosphere, increasing drag, and Skylab fell from orbit largely uncontrolled on July 11, 1979. With the media and diplomatic channels awakened by the Cosmos 954 reentry, there was intense interest. NASA predicted 1 in 152 odds of striking a person. There was still some control over the spacecraft, so NASA attempted to control the reentry by adjusting the station's altitude. This worked, but the station took longer to burn than expected, and there was a 4% error in the calculation — it ended up hitting Australia, strewing debris across Western Australia southeast of Perth. It was the most massive object ever to reenter uncontrolled, tipping the scales at 85 tons. (The Mir space station was more massive, but made a controlled entry over the South Pacific.)

Fragment of Skylab, recovered from the crash site and displayed at the US Space and Rocket Center

Salyut 7

In the 1970s, the Soviet Union launched a series of space stations under the designation "Salyut." All of these heavy spacecraft eventually reentered, but the last of them (and the heaviest) was Salyut 7. Equipped with two docking ports to permit resupply and crew exchange, Salyut 7 had enjoyed a strong career starting in 1982. Near the end of its lifespan, an unmanned TKS spacecraft designated Cosmos 1686 arrived and docked to the station, expanding its pressurized volume and demonstrating the concept of modular stations in preparation for the launch of Mir the following year. In 1986, the first Mir crew made a brief trip to Salyut 7, the last to visit the station. It was then abandoned. On February 7, 1991, the station finally fell from orbit, reentering over Argentina and scattering debris near the town of Capitan Bermudez. With the TKS module attached, the combined system had a mass of 40,000 kg. Unlike its Salyut predecessors, its reentry was completely uncontrolled. More about the Salyut 7 debris, including the scientific analysis of a tank recovered from the crash site, is available here.

Delta II Upper Stage

Many upper stages have reentered through the years; in fact, rocket boosters constitute the majority of large space debris. Most are not observed, but many fragments have been found. In 1997, Ms. Lottie Williams of Tulsa, OK, was hit by a piece of one while she was out walking. It didn't injure her, and the piece was light and cool. It turned out to be fabric insulation from a Delta II rocket's upper stage, which had been launched in 1996 and floated derelict ever since. More of the debris was found downrange, in Texas. Williams is the only person definitively known to have been struck by a piece of reentering orbital debris. You can read more about Lottie Williams here, holding up her small scrap of insulation.

It could have been worse; this tank is from the same rocket, found downrange in Texas.


February 1, 2003. STS-107 was Columbia's first flight in several years, having been sidelined while the other three Orbiters worked on ISS construction. She was scheduled to receive Discovery's Orbiter Docking System, so that she could take over missions while Discovery underwent a routine maintenance period. As she was aging, she was not expected to make many more flights; her last mission was tentatively placed for 2009, returning the Hubble Space Telescope from orbit. (More on that later.) The mission had been a complete success, and it was time to return home. Unbeknownst to NASA or the crew, a piece of foam insulation had punctured one of the reinforced carbon panels. During entry, hot plasma entered through this hole and melted through the aluminum ribs of the wing. The wing eventually tore away, and the entire vehicle rapidly broke up. Debris was scattered over hundreds of miles, and continues to be recovered to this day; last August, the continuing drought in Texas lowered the level of Lake Nacodoches sufficiently to reveal a tank from the fuel cell that provided Columbia with electrical power.

Recovered Columbia debris being identified, processed, and laid out for analysis by the accident investigation board.

Future Reentries

Low Earth orbit is full of objects, the vast majority inactive rocket parts, derelict spacecraft, and fragments. Reentries will keep on happening. The recently deactivated Rossi X-ray Timing Explorer has an estimated 1 in 1,000 chance of injuring a person. The Hubble Space Telescope has no means of returning to Earth under its own power; unless a robotic de-orbit system is developed in time, it will also return uncontrolled, with a 1 in 700 chance of injuring a person, largely due to its massive primary mirror.

Here's what's up there now, in low orbit and zoomed out to geosynchronous orbit. There's more going up all the time, so this will only get busier. Which one will come down next?

Cataloged objects in Low Earth Orbit and out to Geosynchronous Earth Orbit

Anne Dirkse, Flickr // CC BY-SA 2.0
10 Astonishing Things You Should Know About the Milky Way
Anne Dirkse, Flickr // CC BY-SA 2.0
Anne Dirkse, Flickr // CC BY-SA 2.0

Our little star and the tiny planets that circle it are part of a galaxy called the Milky Way. Its name comes from the Greek galaxias kyklos ("milky circle") and Latin via lactea ("milky road"). Find a remote area in a national park, miles from the nearest street light, and you'll see exactly why the name makes sense and what all the fuss is about. Above is not a sky of black, but a luminous sea of whites, blues, greens, and tans. Here are a few things you might not know about our spiraling home in the universe.


The Milky Way galaxy is about 1,000,000,000,000,000,000 kilometers (about 621,371,000,000,000,000 miles) across. Even traveling at the speed of light, it would still take you well over 100,000 years to go from one end of the galaxy to the other. So it's big. Not quite as big as space itself, which is "vastly, hugely, mind-bogglingly big," as Douglas Adams wrote, but respectably large. And that's just one galaxy. Consider how many galaxies there are in the universe: One recent estimate says 2 trillion.


artist's illustration of the milky way galaxy and its center
An artist's concept of the Milky Way and the supermassive black hole Sagittarius A* at its core.
ESA–C. Carreau

The Milky Way is a barred spiral galaxy composed of an estimated 300 billion stars, along with dust, gas, and celestial phenomena such as nebulae, all of which orbits around a hub of sorts called the Galactic Center, with a supermassive black hole called Sagittarius A* (pronounced "A-star") at its core. The bar refers to the characteristic arrangement of stars at the interior of the galaxy, with interstellar gas essentially being channeled inward to feed an interstellar nursery. There are four spiral arms of the galaxy, with the Sun residing on the inner part of a minor arm called Orion. We're located in the boondocks of the Milky Way, but that is OK. There is definitely life here, but everywhere else is a question mark. For all we know, this might be the galactic Paris.


If you looked at all the spiral galaxies in the local volume of the universe, the Milky Way wouldn't stand out as being much different than any other. "As galaxies go, the Milky Way is pretty ordinary for its type," Steve Majewski, a professor of astronomy at the University of Virginia and the principal investigator on the Apache Point Observatory Galactic Evolution Experiment (APOGEE), tells Mental Floss. "It's got a pretty regular form. It's got its usual complement of star clusters around it. It's got a supermassive black hole in the center, which most galaxies seem to indicate they have. From that point of view, the Milky Way is a pretty run-of-the-mill spiral galaxy."


On the other hand, he tells Mental Floss, spiral galaxies in general tend to be larger than most other types of galaxies. "If you did a census of all the galaxies in the universe, the Milky Way would seem rather unusual because it is very big, our type being one of the biggest kinds of galaxies that there are in the universe." From a human perspective, the most important thing about the Milky Way is that it definitely managed to produce life. If they exist, the creatures in Andromeda, the galaxy next door (see #9), probably feel the same way about their own.


John McSporran, Flickr // CC BY 2.0

We have a very close-up view of the phenomena and forces at work in the Milky Way because we live inside of it, but that internal perspective places astronomers at a disadvantage when it comes to determining a galactic pattern. "We have a nice view of the Andromeda galaxy because we can see the whole thing laid out in front of us," says Majewski. "We don't have that opportunity in the Milky Way."

To figure out its structure, astronomers have to think like band members during a football halftime show. Though spectators in the stands can easily see the letters and shapes being made on the field by the marchers, the band can't see the shapes they are making. Rather, they can only work together in some coordinated way, moving to make these patterns and motions on the field. So it is with telescopes and stars.


Interstellar dust further stymies astronomers. "That dust blocks our light, our view of the more distant parts of the Milky Way," Majewski says. "There are areas of the galaxy that are relatively obscured from view because they are behind huge columns of dust that we can't see through in the optical wavelengths that our eyes work in." To ameliorate this problem, astronomers sometimes work in longer wavelengths such as radio or infrared, which lessen the effects of the dust.


Astronomers can make pretty reasonable estimates of the mass of the galaxy by the amount of light they can see. They can count the galaxy's stars and calculate how much those stars should weigh. They can account for all the dust in the galaxy and all of the gas. And when they tally the mass of everything they can see, they find that it is far short of what is needed to account for the gravity that causes the Milky Way to spin.

In short, our Sun is about two-thirds of the way from the center of the galaxy, and astronomers know that it goes around the galaxy at about 144 miles per second. "If you calculate it based on the amount of matter interior to the orbit of the Sun, how fast we should be going around, the number you should get is around 150 or 160 kilometers [93–99 miles] per second," says Majewski. "Further out, the stars are rotating even faster than they should if you just account for what we call luminous matter. Clearly there is some other substance in the Milky Way exerting a gravitational effect. We call it dark matter."


Dark matter is a big problem in galactic studies. "In the Milky Way, we study it by looking at the orbits of stars and star clusters and satellite galaxies, and then trying to figure out how much mass do we need interior to the orbit of that thing to get it moving at the speed that we can measure," Majewski says. "And so by doing this kind of analysis for objects at different radii across the galaxy, we actually have a fairly good idea of the distribution of the dark matter in the Milky Way—and yet we still have no idea what the dark matter is."


andromeda galaxy
The Andromeda galaxy
ESA/Hubble & NASA

Sometime in the next 4 or 5 billion years, the Milky Way and Andromeda galaxies will smash into each other. The two galaxies are about the same size and have about the same number of stars, but there is no cause for alarm. "Even though there are 300 billion stars in our galaxy and a comparable number, or maybe more, in Andromeda, when they collide together, not a single star is expected to hit another star. The space between stars is that vast," says Majewski.


There are countless spacecraft and telescopes studying the Milky Way. Most famous is the Hubble Space Telescope, while other space telescopes such as Chandra, Spitzer, and Kepler are also returning data to help astronomers unlock the mysteries of our swirling patch of stars. The next landmark telescope in development is NASA's James Webb Space Telescope. It should finally launch in 2019. Meanwhile, such ambitious projects as APOGEE are working out the structure and evolution of our spiral home by doing "galactic archaeology." APOGEE is a survey of the Milky Way using spectroscopy, measuring the chemical compositions of hundreds of thousands of stars across the galaxy in great detail. The properties of stars around us are fossil evidence of their formation, which, when combined with their ages, helps astronomers understand the timeline and evolution of the galaxy we call home. 

Mysterious 'Hypatia Stone' Is Like Nothing Else in Our Solar System

In 1996, Egyptian geologist Aly Barakat discovered a tiny, one-ounce stone in the eastern Sahara. Ever since, scientists have been trying to figure out where exactly the mysterious pebble originated. As Popular Mechanics reports, it probably wasn't anywhere near Earth. A new study in Geochimica et Cosmochimica Acta finds that the micro-compounds in the rock don't match anything we've ever found in our solar system.

Scientists have known for several years that the fragment, known as the Hypatia stone, was extraterrestrial in origin. But this new study finds that it's even weirder than we thought. Led by University of Johannesburg geologists, the research team performed mineral analyses on the microdiamond-studded rock that showed that it is made of matter that predates the existence of our Sun or any of the planets in the solar system. And, its chemical composition doesn't resemble anything we've found on Earth or in comets or meteorites we have studied.

Lead researcher Jan Kramers told Popular Mechanics that the rock was likely created in the early solar nebula, a giant cloud of homogenous interstellar dust from which the Sun and its planets formed. While some of the basic materials in the pebble are found on Earth—carbon, aluminum, iron, silicon—they exist in wildly different ratios than materials we've seen before. Researchers believe the rock's microscopic diamonds were created by the shock of the impact with Earth's atmosphere or crust.

"When Hypatia was first found to be extraterrestrial, it was a sensation, but these latest results are opening up even bigger questions about its origins," as study co-author Marco Andreoli said in a press release.

The study suggests the early solar nebula may not have been as homogenous as we thought. "If Hypatia itself is not presolar, [some of its chemical] features indicate that the solar nebula wasn't the same kind of dust everywhere—which starts tugging at the generally accepted view of the formation of our solar system," Kramer said.

The researchers plan to further probe the rock's origins, hopefully solving some of the puzzles this study has presented.

[h/t Popular Mechanics]


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