Cause for celebration! The 10,000th near-Earth object (NEO) has been discovered.

Asteroid 2013 MZ5 joined the ranks of asteroids and comets whose orbits pass near Earth. On an astronomical scale, “near” means within 28 million miles…

The Near-Earth Object Program looks for all NEOs, especially large ones with the potential to harm Earth (called a Potentially Hazardous Asteroid). This type of candidate would need to be at least about 100 feet (about 30 meters) across to do significant damage a populated area—and about 3,200 feet (nearly a kilometer) in diameter to cause global devastation.

As you might expect, large asteroids are easier to find than small ones. NASA estimates that we have discovered all but a few dozen of the largest asteroids, those 460 feet (140 meters) in diameter or larger. (Whew!) Therefore, NASA is shifting its attention to medium-sized threats. If 90% of these were found, the threat of an unexpected impact would be greatly reduced, perhaps even to one percent!

“Finding 10,000 near-Earth objects is a significant milestone,” said Lindley Johnson, program executive for NASA’s Near-Earth Object Observations Program. “But there are at least 10 times that many more to be found before we can be assured we will have found any and all that could impact and do significant harm to the citizens of Earth.”

Discovered by the Pan-STARRS-1 telescope in Hawaii, this new asteroid is about 1,000 feet in diameter. That would put it in a pretty dangerous category if it were headed toward Earth, but its orbit does not pass close enough to us to be a significant threat.

“The first near-Earth object was discovered in 1898,” said Don Yeomans, manager of the Near-Earth Object Program Office at NASA’s Jet Propulsion Laboratory. “Over the next hundred years, only about 500 had been found. But then, with the advent of NASA’s NEO Observations program in 1998, we’ve been racking them up ever since. And with new, more capable systems coming on line, we are learning even more about where the NEOs are currently in our solar system, and where they will be in the future.”

A privately-funded mission called Sentinel might extend the search with a space-based telescope that will likely identify hundreds of thousands of NEOs. You can watch Science Today story on Sentinel or watch an animation narrated by former astronaut Ed Lu describing the mission.

10,000 down, how many to go…?

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: PS-1/UH

Every time an asteroid comes close to Earth, we learn something new about our Universe. With its closest approach last week, we learned that asteroid 1998 QE2 has its own moon.

Astronomers use close approaches by asteroids to take pictures and measurements that tell us more about space objects. On the scale of the solar system, apparently 3.6 million miles (about 15 times the distance between Earth and the Moon) is considered a “close approach.” Close-approach studies depend on the 70-meter Deep Space Network (DSN) antenna in Goldstone, California, with additional imagery supplied from other antennas in the DSN to maximize information content.

At this distance, the DSN was able to resolve a moon orbiting around asteroid 1998 QE2. As such, it is classified as a binary asteroid.  According to NASA, over 15% of asteroids travel in groups, where two or three objects orbit around one another.

The detailed study of asteroid 1998 QE2 marks a milestone in NASA’s Near Earth Object Program. “It’s one of the initial successes of our effort to find the big asteroids that could hit the Earth and cause global catastrophe,” said Paul Chodas, a scientist who is part of the Program.

The asteroid is not dangerous or threatening to earth, but astronomers can nonetheless use its close approach and that of others as valuable learning opportunities.

“Whenever an asteroid approaches this closely, it provides an important scientific opportunity to study it in detail to understand its size, shape, rotation, surface features, and what they can tell us about its origin. We will also use new radar measurements of the asteroid’s distance and velocity to improve our calculation of its orbit and compute its motion farther into the future than we could otherwise,” said Lance Benner, the principal investigator for the Goldstone radar observations at the Jet Propulsion Laboratory in Pasadena, California.

The more asteroids we catalog, the safer we are from a potentially dangerous impact. See our video on the B612’s Sentinel Mission for more information.

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA/JPL-Caltech/GSSR

Early on the morning of April 29, 2013, Commander Chris Hadfield’s residence got hit by a rock. Sounds like a story for a slow day on local news, except that Hatfield lives 225 miles above Earth in the International Space Station (ISS), and the offending rock was not thrown by vandals—it was merely passing by.

The rock in question is most likely just one of a huge number of similar pebbles that occupy our part of the Solar System. If you were to hold such an object in your hand, it would hardly seem threatening, but with gravity to accelerate it and without a thick layer of atmosphere to slow it down, these tiny objects can endanger spacefarers such as Hadfield.

Reaching speeds of 25,000 miles per hour, these rocks zip along between 12 and 20 times faster than a speeding bullet (depending on the bullet)!

Luckily, the object did not hit the main body of the space station, but it did punch a small hole in part of the ISS’s acre of photovoltaic solar panels. And while the station does sport various types of impact-resistant shielding, it could still be vulnerable to a larger object.

There have never been any lives lost due to an impact in space, but the Near Earth Object hunters at the B612 Foundation posted an ominous (and succinct) reminder to Facebook minutes after the event: “Definitely NOT good.”

It is estimated that hundreds of tons of similar objects fall to Earth every day, but with an ever-increasing presence beyond Earth’s protective atmosphere, current and future space explorers must be acutely alert to these potentially harmful rocks. We live in a densely populated part of the universe and have to remain vigilant.

Josh Roberts is a program presenter and astronomer at the California Academy of Sciences. He also contributes content to Morrison Planetarium productions.

If geochronology is “the science of determining the ages of earth materials” (according to the center’s website), then Renne must know his gnat’s eyebrow. For those of us lay-folk, it’s about 5,000 years.

Renne and his colleagues have a new paper in Science pinpointing the dates of both the impact and the dinosaur extinction, placing them within the same time of each other—providing evidence, once again, for an asteroid or comet impact being the cause of extinction.

The 110 mile-wide Chicxulub (cheek’-she-loob) crater, off the Yucatan coast of Mexico, is likely the result of a six-mile in diameter asteroid or comet. Using and refining a technique called argon-argon dating, the scientists determined that the impact occurred 66,038,000 years ago, plus or minus 11,000 years.

The same argon-argon dating put the dinosaur extinction at 66,043,000 years ago, with the same margin of error.

The first link between the impact event and dinosaur extinction was published in 1980 by UC Berkeley’s Luis and Walter Alvarez. Since then, many other scientists have supported or refuted the theory, sometimes putting the extinction several hundred thousand years before the impact.

“When I got started in the field, the error bars on these events were plus or minus a million years,” says UC Berkeley paleontologist William Clemens. “It’s an exciting time right now, a lot of which we can attribute to the work that Paul and his colleagues are doing in refining the precision of the time scale with which we work.”

Despite the synchronous impact and extinction, Renne cautions that the impact was not the sole cause of extinction. Dramatic climate variation over the previous million years, including long cold snaps amidst a general Cretaceous hothouse environment, probably brought many creatures to the brink of extinction, and the impact kicked them over the edge.

“These precursory phenomena made the global ecosystem much more sensitive to even relatively small triggers, so that what otherwise might have been a fairly minor effect shifted the ecosystem into a new state,” Renne says. “The impact was the coup de grace.”

Mining asteroids for precious resources sounds like something straight out of a science fiction novel. But the first steps toward such grand missions are already underway—and not by organizations you might think of first.

Since exploration became a reality with the launch of Sputnik in 1957, governments have acted as the primary driving force (and funding source) for such spacy endeavors. But that’s beginning to change. A recent announcement by Deep Space Industries declared their intentions to compete with Planetary Resources and successfully mine asteroids in the next decade.

Planetary Resources’ announcement last April was met with some skepticism by the public. However, the concept no longer sounds so lofty. Billionaires and corporations quickly came forward to invest in the project and provide more significant funding than a government-sponsored project. And along with the money came talent: specialists brought on include former astronauts, asteroid specialists, and an operational director of Mars lander missions, even James Cameron.

Why the interest in asteroids?  They’re a hot topic in the scientific community. NASA’s Dawn mission is exploring two of the largest asteroids up close. And President Obama has indicated asteroids should be our next target for manned spaceflight instead of the Moon or even Mars. Additionally, the privately-funded non-profit B612 Foundation is preparing to launch the Sentinel observatory, designed to map out Near Earth Objects and the inner Solar System in the next couple years.

While they are intriguing objects in our Solar System, asteroids are also potentially hazardous—especially if one happens to be on a collision course with Earth. Just ask the dinosaurs—we would much prefer to find them before they find us.

Asteroids aren’t ordinary rocks! They contain metals such as iron, nickel, platinum, gold, manganese, molybdenum, tungsten, and others, all of which exist in Earth’s crust because they were brought by asteroids during our planet’s early years. Many also harbor ice. We can potentially harvest these resources to supplement materials on Earth or to utilize in future space endeavors.

In fact, one of the key aspects of space mining is that the resources probably won’t come back to Earth. Rather, they would remain in low Earth orbit and be used for space-based projects like refueling aging satellites and in-space manufacturing. Considering that it costs an estimated $10,000 per pound of material to put something into put space, having the resources already there would save considerable financial and physical strain. Extracting the resources provides challenges, too, however: for example, platinum-rich chondritic or iron body contains only around one ounce of platinum per ton.

Both companies are proposing three-phase projects that consist of tracking asteroids and assessing their resource potential, sending investigative missions, and eventually, initiating robotic mining. However, Planetary Resources has a few billion dollars more money than Deep Space Industries and almost a year’s head start.

Government-funded missions blazed the earliest trails in space exploration, but more and more private industrialists are imagining the next frontier. It looks like the next wave of exploration and discovery will arise from the private sector.

Elise Ricard holds a master’s degree in museum education and is a presenter at the Morrison Planetarium.

Image: Planetary Resources

Two researchers hypothesize that an asteroid belt, just the right size and distance from its star, might be necessary for a star system to support a life-bearing planet.

This might sound surprising, since asteroids can occasionally impact Earth and trigger mass extinctions. Ouch! But an emerging view proposes that asteroid collisions with planets may provide a boost to the birth and evolution of complex life.

For one thing, asteroids delivered water and organic compounds to the early Earth. Consistent with the theory of punctuated equilibrium, occasional asteroid impacts might also accelerate the rate of biological evolution by disrupting a planet’s environment to the point that species must evolve new adaptation strategies.

Rebecca Martin, of the University of Colorado, and Mario Livio, of the Space Telescope Science Institute, looked at our solar system and used theoretical models and actual observations of other star systems and exoplanets to study the theory that life needs an asteroid belt.

They suggest that the location of an asteroid belt relative to a Jupiter-like planet is particularly favorable to life. The asteroid belt in our solar system, located between Mars and Jupiter, is a region of millions of space rocks sitting near the “snow line,” beyond which volatile materials such as water ice are far enough from the Sun’s heat to remain intact.

Our solar system’s formation was just right for life, Livio says. “To have such ideal conditions you need a giant planet like Jupiter that is just outside the asteroid belt [and] that migrated a little bit, but not through the belt,” he explains. “If a large planet like Jupiter migrates through the belt, it would scatter the material. If, on the other hand, a large planet did not migrate at all, that, too, is not good because the asteroid belt would be too massive. There would be so much bombardment from asteroids that life may never evolve.”

Using our solar system as a model, Martin and Livio proposed that asteroid belts in other solar systems would always be located approximately at the snow line. They created models of protoplanetary disks, the dense gas and dust around a newly formed star; then they looked at observations from NASA’s Spitzer Space Telescope of 90 such regions that have warm dust, which could indicate the presence of an asteroid belt-like structure. The warm dust fell right near the snow line.

But for life to exist, the system also needs a large gas giant, like Jupiter, to “manage” the size of the asteroid belt. So Martin and Livio looked at data for 520 giant planets found outside our solar system. Only 19 of them reside outside the snow line, suggesting that most of the giant planets that formed outside the snow line have migrated too far inward to preserve the right-sized asteroid belt needed to foster life on an Earth-like planet near the belt. The team calculated that less than four percent of the observed systems may actually harbor such a compact asteroid belt.

“Our study shows that only a tiny fraction of planetary systems observed to date seem to have giant planets in the right location to produce an asteroid belt of the appropriate size, offering the potential for life on a nearby rocky planet,” says Martin. “Our study suggests that our solar system may be rather special.”

Their findings are published in the Monthly Notices of the Royal Astronomical Society: Letters.

Image: NASA, ESA, and A. Feild (STScI)

The third Thursday of every month, the Morrison Planetarium hosts “Universe Update” at the 6:30 planetarium show during NightLife. I select my favorite astronomy stories from the past month, and I give a brief run-down of current discoveries while taking audiences on a guided tour of the Universe. As you may or may not know, the planetarium sports a three-dimensional atlas of the Universe, so we can take you places virtually while talking about the latest astronomy news.

I always start at Earth and work my way out to cosmological distances, so I’ll list the news stories in the same order—from closest to farthest from home.

Fourth graders from the Emily Dickinson Elementary School in Bozeman, Montana, proved themselves more creative than NASA engineers! Crazy rocket scientists named their two lunar-orbiting spacecraft “GRAIL-A” and “GRAIL-B” (where, of course, “GRAIL” is an acronym, which stands for “Gravity Recovery and Interior Laboratory”). The elementary school students selected the names “Ebb” and “Flow,” which NASA selected as the winning contribution in a nationwide contest. The GRAIL mission measures the ebb and flow of gravity, in a sense, as the two spacecraft orbit the Moon and measure variations in its gravitational pull. From the GRAIL website:

As they fly over areas of greater and lesser gravity, caused both by visible features such as mountains and craters and by masses hidden beneath the lunar surface, they will move slightly toward and away from each other. An instrument aboard each spacecraft will measure the changes in their relative velocity very precisely, and scientists will translate this information into a high-resolution map of the Moon’s gravitational field.

A little farther from home, new reports from a comet impact on the Sun that took place last July. We like to describe comets as “dirty snowballs,” and as you might imagine, a comet getting too close to the Sun stands a snow ball’s chance in… Well, a million-degree plasma irradiated by incident solar flux. The comet evaporated over a period of about 20 minutes, and as described in a paper that appears in today’s Science magazine, it probably measured between 150 and 300 feet across and had a mass equivalent to an aircraft carrier. According to Karel Schrijver, a solar scientist at Lockheed Martin in Palo Alto, the comet moved speedily to its demise: “It was moving along at almost 400 miles per second through the intense heat of the Sun—and was literally being evaporated away.”

A fair bit farther from the scorching heat of the Sun, the Dawn spacecraft is sending back gorgeous images of the asteroid Vesta, including this gorgeous snapshot of a crater on the asteroid’s surface. Dawn has entered a low-altitude orbit that gives it a close look at the potato-shaped planetoid. Learning more about such objects should help us better understand the formation of the solar system, and after its stay at Vesta, Dawn will move on to Ceres, the dwarf planet (like Pluto) that resides between the orbits of Mars and Jupiter.

Beyond our own solar system, of course, we are rapidly discovering planets in orbit around other stars: these extrasolar planets (or exoplanets) now number in excess of 700, and astronomers find more all the time.

As I described in one of my updates from the American Astronomical Society meeting last week, astronomers have announced the discovery of the most compact extrasolar planetary system yet detected. Looking at the KOI 961 system side-by-side with Jupiter and its major satellites strikes me as a particularly illuminating comparison: only 70% larger than Jupiter, the host star (the smallest known to have planets) has at least three planets (the smallest yet found) in orbit around it, the smallest of which is about the size of Mars. John Johnson, an astronomer at Caltech, announced the superlative system last week, and on April 2nd, he will give a talk in the Morrison Planetarium as part of our Benjamin Dean Lecture Series, “The Quest for Habitable Planets Orbiting Red Dwarfs.”

And astronomers have help in their search. Just this week, we had a glimpse into the democratization of astronomy… Viewers of a British television program(me) may have discovered a new exoplanet! Evidence from the Kepler mission suggests the existence of a Neptune-sized planet around the star SPH10066540, orbiting every 90 days at a distance equivalent to Mercury from our Sun. The discovery awaits confirmation, but you don’t have to watch telly in the U.K. to join in the search for such objects. You can go to the PlanetHunters website and start sifting through Kepler data in hopes of finding a planet of your own…

In another of my posts last week, I mentioned the spectacular new Spitzer image of Cygnus X, a massive star-forming region in the constellation (you guessed it) Cygnus. Ten times the size of the Orion Molecular Cloud Complex, Cygnus X appears to host some 26,000 possible young stellar objects, according to an announcement last week.

Moving farther from home, I talked a bit about the new dark matter map that I previously described in a post from Austin. It turns out that analyzing the light from 10 million galaxies call tell you a lot about where dark matter resides, and since dark matter drives the formation of much of the structure in the Universe, that knowledge helps us understand more about the evolution of the cosmos…

The dark matter maps tell one part of the story, but we also rely on studies of the cosmic microwave background to tease out how the Universe has evolved over time. Since 2003, the gold standard of such measurements have come from the Wilkinson Microwave Anisotropy Probe (WMAP). But ESA’s Planck mission recently completed its survey of the cosmic microwave background: the sensor used to make the observations ran out of its coolant a little less than a week ago. It had collected more than two years’ worth of data, however, and the first new high-resolution maps will be released early next year. (Hey! It takes a while to process all that data.)

That’s all for now. Check back for next month’s update! Or come to NightLife on Thursday, 15 February, and check out “Universe Update” live in the Morrison Planetarium.

Ryan Wyatt is the director of the Morrison Planetarium and Science Visualization at the California Academy of Sciences.

Image: SOHO (ESA & NASA)

So imagine the surprise, forty years ago, when the Apollo astronauts brought back moon rocks with magnetic properties. How is that possible?

This week, two teams of scientists attempt to solve the mystery with separate papers in Nature.

Christina Dwyer, of UC Santa Cruz, and her team offer one theory. Early in its history, the Moon orbited Earth at a much closer distance than it does now, and it continues to gradually recede from Earth—even today! At close distances, tidal interactions between Earth and the Moon caused the Moon’s mantle to rotate slightly differently than the core. This differential motion of the mantle relative to the core stirred the liquid core, creating fluid motions that could give rise to a magnetic field.

Michael Le Bars, of Non-Equilibrium Phenomena Research Institute in Marseille, France, and his team have another theory. Large impact events like asteroids a few billion years ago could have caused sloshing within the lunar core for up to 10,000 years at a time.

So is it the asteroids’ fault or Earth’s? New Scientist doesn’t take sides:

Both models offer “a way out of a pretty major conundrum,” says Ben Weiss at the Massachusetts Institute of Technology.

Both theories produce a magnetic field of the right strength—about one fiftieth of what we experience here on Earth’s surface—but how do we decide which one is correct?  Sky & Telescope explains:

Distinguishing between these theories will depend in part on figuring out which rocks were magnetized when. Big bull’s-eyes happened pretty rarely in lunar history. If an impact created a dynamo, any molten surface rock around the time of the crash—such as lava created by the hit itself—would record the magnetic field created. But lava that erupted on the surface between these infrequent events wouldn’t. If most lunar rocks everywhere were magnetized during a particular time period, including rocks not made by impacts, that would sway the balance toward the precession argument, Weiss says. If impact melts are always associated with a magnetic field, the balance swings the other way.

Or maybe a combination of both? Wired makes the point that the two ideas aren’t mutually exclusive:

Dwyer herself has suggested that both models could have some parts correct, with tidal forces pushing the mantle steadily for a time and giant impacts speeding up the motion occasionally.

Image: Luc Viatour / www.Lucnix.be

Now, new evidence, published last week in Nature, supports the theory that comets delivered a significant portion of Earth’s oceans, which scientists believe formed about 8 million years after the planet itself.

“Life would not exist on Earth without liquid water, and so the questions of how and when the oceans got here is a fundamental one,” says University of Michigan astronomer Ted Bergin. “It’s a big puzzle and these new findings are an important piece.”

Bergin is a co-investigator on HiFi, the Heterodyne Instrument for the Infrared on the Hershel Space Observatory. With measurements from HiFi, the researchers found that the ice on a comet called Hartley 2 has the same chemical composition as our oceans. Both have similar D/H ratios. The D/H ratio is the proportion of deuterium, or heavy hydrogen, in the water. A deuterium atom is a hydrogen with an extra neutron in its nucleus.

This was the first time ocean-like water was detected in a comet. “We were all surprised,” admits Bergin.

Six other comets HiFi measured in recent years had a much different D/H ratio than our oceans, meaning similar comets could not have been responsible for more than 10 percent of Earth’s water.

The astronomers hypothesize that Hartley 2 was born in a different part of the solar system than the other six. Hartley most likely formed in the Kuiper belt, which starts near Pluto at about 30 times farther from the sun than Earth is. The other six hail from the Oort Cloud more than 5,000 times farther out.

“The results show that the amount of material out there that could have contributed to Earth’s oceans is perhaps larger than we thought,” speculates Bergin.

Image courtesy of NASA

Vesta is actually an asteroid, one of the largest in the solar system. Since mid-July, NASA’s Dawn mission has been orbiting and imaging what is possibly the oldest planetary surface in the solar system.

The rather potato-shaped Vesta measures about 578 by 560 by 458 kilometers (359 by 348 by 285 miles): “too small and odd-shaped to qualify as a dwarf planet,” according to Scientific American. Yet scientists are astounded at its planet-like features.

“We are learning many amazing things about Vesta, which we call the smallest terrestrial planet,” said Chris Russell, the Dawn Principal Investigator. “Like Earth, Mars, Venus and Mercury, Vesta has ancient basaltic lava flows on the surface and a large iron core. It has tectonic features, troughs, ridges, cliffs, hills and a giant mountain.”

That giant mountain could be an understatement! At 20 kilometers in height (over 65,000 feet), “The south polar mountain is larger than the big island of Hawaii, the largest mountain on Earth, as measured from the ocean floor,” Russell explained. “It is almost as high as the highest mountain in the solar system, the shield volcano Olympus Mons on Mars.”

The surface of Vesta shows the ravages of time. Many more craters are seen in the northern hemisphere than the southern because an enormous impact altered the earlier cratering record in the south. (Check out the familiar-looking “Snowman” crater on Discover’s Bad Astronomy blog.) “The team is now measuring the craters, identifying ridges, hills and lineations to have the sunlit surface totally mapped by the end of the year,” said Russell.

Astronomers find the difference in the cratering between the two hemispheres quite striking (so to speak). By counting the number of craters per unit area in different regions, astronomers can estimate the relative ages of the different terrains. Preliminary results of these crater age dates indicate much younger ages for areas in the south versus the north, as young as 1-2 billion years old. So far, the oldest ages, in the northern hemisphere, are younger than 4 billion years old—an unexpected result given that meteorites from Vesta have ages of 4 billion years! However, more detailed data will eventually allow refinement of the crater counts, and the assumptions about how the impact flux (or rate of impacts) decreases with time will be evaluated, so the absolute ages are preliminary.

Scientific American reports on the importance of studying Vesta:

The asteroid made a particularly interesting target for Dawn because the space rock carries evidence of the history of much of the solar system as well. Vesta-derived meteorites that landed on Earth allowed planetary scientists to measure the asteroid’s age in the laboratory, showing that it is one of the oldest large bodies in the solar system… As such, Vesta provides a valuable lab for studying the materials and processes that formed the planets during the first millions of years in the early solar system.

Image: NASA/JPL/Dawn