Fragments of the Sutter’s Mill meteorite fall collected by astronomer Dr. Peter Jennisken. (NASA)

Researchers have struck scientific gold at Sutter’s Mill, site of the famed California Gold Rush where the precious metal was first discovered in 1848.

In April of this year, the scientists recovered a rare meteorite which contains clues to the early history of the solar system.

Using Doppler radar, the same technology used by weather forecasters, the scientists detected a shower of meteors raining down over the communities of Coloma and Lotus, just after the asteroid broke up in the atmosphere.

That allowed scientists to, for the first time,  quickly find, recover and study a primitive meteorite that had little exposure to the elements.

It’s the most pristine look at the surface of ancient asteroids scientists have been able to study so far. Because of the rapid recovery of materials, scientists were able to detect compounds that quickly disappear once a meteorite hits Earth.

Reporting in Science, the researchers say their rare find was classified as a Carbonaceous-Mighei or CM-type carbonaceous chondrite meteorite, which is known to contain water and complex organic compounds, such as amino acids, molecules that help form life.

But, according to NASA’s Danny Glavin, he and the other scientists weren’t able to detect many of the amino acids in their find because it appeared the samples had been heated in space before arriving on Earth.

“The small three meter-sized asteroid that impacted over California’s Sierra Nevada came in at twice the speed of typical meteorite falls,” said lead author Peter Jenniskens, of the SETI Institute and NASA’s Ames Research Center, both located in California. “Clocked at 64,000 miles per hour, it was the biggest impact over land since the impact of the four meter-sized asteroid 2008 TC3, four years ago over Sudan.”

The scientists also say that, for the first time, they were able to identify the region of space where these types of meteorites come from.

After studying photographs and video of the asteroid, Jenniskens figured that it came in on an unusually low-angled orbit, more like a comet‘s orbit, passing closer to the sun than what has been learned from past recorded meteorite falls.

Scientists found the asteroid, as it was in orbit, was influenced by the gravity of both the Sun and Jupiter at times.

“It circled the sun three times during a single orbit of Jupiter, in resonance with that planet,” Jenniskens said.

A meteor flashes across the sky during the peak of the November 2009 Leonid Meteor Shower. (Photo: Ed Sweeney via Wikimedia Commons)

The asteroid that spawned the meteorite was estimated to be around 45359 kg.  Of that, less than 1kg was actually recovered on the ground in the form of 77 tiny meteorites. The biggest of those meteorites was 205 grams.

While the scientists didn’t find much actual gold in the Sutter’s Mill meteorite, about 150 parts per billion, it was still “scientific gold,” according to co-author and cosmochemist Qing-zhu Yin of the University of California at Davis.

“With 78 other elements measured, Sutter’s Mill provides one of the most complete records of elemental compositions documented for such primitive meteorites,” he said.

S/2010 J 1 in motion Sept. 8, 2010. Animation is sped up by a factor of 2000. The actual time between each image in the animation is roughly 38 minutes. (Photo:Canada-France-Hawaii Telescope)

Astronomers have found that one of two recently-discovered moons of Jupiter is just two kilometers in diameter and may be the smallest of Jupiter’s 67 satellites.

Back in September 2010, scientists discovered two unknown distant satellites of Jupiter while conducting routine tracking observations of the planet’s previously identified moons.

To confirm that these were indeed new satellites of Jupiter, and not asteroids, the scientists re-observed them several more times during the autumn of 2010.

The International Astronomical Union’s Minor Planet Center designated the two new moons as S/2010 J 1 and S/2010 J 2.

S/2010 J 1 was discovered in September 2010 from images taken with the Palomar Observatory’s 200-inch Hale Telescope.  At its furthest, this moon is about 30,774,922 kilometers from Jupiter.

The second moon, S/2010 J 2, about 26,541,445 kilometers from the giant planet, was discovered the same month on images taken with the MegaCam mosaic CCD camera by the 3.6m Canada-France-Hawaii telescope (CFHT).  After checking observational data, astronomers also later found that the satellite was weakly visible, on Sept 7, 2010, at the Palomar Observatory.

It’s interesting to note that the moon that would come to be called S/2010 J 1, was first detected back in 2003, but was never classified as a satellite because it couldn’t be found in required follow-up observations.

The astronomers say the size of the two moons can be estimated on factors that are based on their brightness.  S/2010 J 1 is estimated to be around three kilometers in diameter. S/2010 J 1, the faintest and probably smallest Jovian moon, has been estimated to be about two kilometers in diameter.

Red diamonds show the 2010-11 observed locations of S/2010 J 1, while blue triangles show the locations of S/2010 J 2. The predicted positions of the satellites for the best fit orbits from JPL are plotted at 48-hour intervals, shown by the red and blue dots for S/2010 J 1 and S/2010 J 2, respectively (Courtesy: Mike Alexandersen)

S/2010 J 1 and S/2010 J 2 are designated as irregular satellites, or provisional moons, and are not given actual names by the International Astronomy Union (IAU) because their discoveries have not been confirmed.

Moons such as the S/2010 J 1 and S/2010 J 2 have been found to be clustered in families of other satellites with similar colors and orbits. Scientists believe these families may have formed as a result of ancient collisions with comets or asteroids with former larger moons.

S/2010 J 1 appears to belong to the Carme group, or family, while S/2010 J 2 appears to belong to the Ananke group.

NASA finds there are more potentially hazardous asteroids (PHA)s, closely aligned with the plane of our solar system than previous models suggested. (Image: NASA/JPL-Caltech)

First, the good news. There are fewer asteroids near Earth than previously estimated.  Now the bad news. A new NASA survey also finds there may be more than twice as many aligned with Earth’s orbit than thought, which could increase the odds of an asteroid coming close enough to us to cause concern.

The findings from NASA/JPL’s Near Earth Object Wide-field Infrared Explorer (NEOWISE) project also reveal new information about the origins and possible dangers these space objects might pose.

Potentially hazardous asteroids, or PHA’s, are a subset of a larger group of near-Earth asteroids,  which come within eight million kilometers of us and are big enough to pass through Earth’s atmosphere, causing a great amount of damage.

To get a count on how many of these possible troublemakers are out there, NASA used one of its space telescopes to make an assessment of our solar system’s population of PHA’s.

WISE, an unmanned satellite carrying an infrared heat-sensitive telescope, was launched in December 2009 and spent a little over a year imaging the entire sky to provide data on asteroids, the coolest and dimmest stars, and the most radiant galaxies.

Approximately 4,700 PHAs, give or take about 1,500, with diameters larger than 100 meters, were found, according to NEOWISE principal investigator Amy Mainzer.

Most of the asteroids in our solar system never get close to Earth.  They’re found in what’s called the Asteroid Belt, which is between the orbits of Mars and Jupiter.

Scientists think these asteroids may have been fragments that were trying to come together to form a planet when the solar system was forming.  However,  the overwhelming gravitational influence of Jupiter was so strong, it kept the planet from forming.

But, occasionally, if there is an interaction with one of the giant planets, some of the asteroids may be forced to wander away from the main belt and into near-Earth space – causing concern for those of here on terra firma.

To make their tally, Mainzer along with her colleagues at JPL examined approximately 107 PHA’s with WISE telescope data, providing them with a representative sample of the total population of these potentially dangerous objects.

From that sample, Mainzer’s team was able to calculate the total number of PHA’s in the solar system.

This diagram illustrates the differences between orbits of a typical near-Earth asteroid (blue) and a potentially hazardous asteroid (PHA) (orange). (Image: NASA/JPL-Caltech)

Of course, the big question remains how likely is it that one of these potentially-hazardous asteroids actually could strike Earth.   Mainzer, looking back at Earth’s history, points out that major asteroid strikes very rarely happen.  Scientists estimate that such a major hit happens every 100 million years or so.  The last mammoth asteroid collided with Earth about 65 million years ago, causing, scientists think, the extinction of most life on our planet, including the dinosaurs.

Mainzer says astronomers have already discovered most of the significant asteroids out there.  However, she warns, there are many smaller asteroids, which haven’t been discovered yet.  The NEOWISE study indicates that only between 20 and 30 percent of these have been discovered so far.

To keep us safer from asteroid impacts, Mainzer says the most important thing that we can do is actually go look for them.  “Because, if you don’t know where they are, you have no idea how to really deal with any risk,” she says.

Mainzer and her colleagues are currently working on a proposal to build and carry out an advanced survey mission.  Called the Near Earth Object Camera (NEOCam), this proposed mission would locate many more asteroids to provide a more accurate picture of the total asteroid population.

Dr. Amy Mainzer joins us on this week’s radio edition of Science World.  Check out the right column for scheduled air-times or listen to the interview with Dr. Mainzer below.

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Other stories we cover on the “Science World” radio program this week include:

• Success! Privately-funded cargo spacecraft docks with the ISS
• Recommendation to halt prostate cancer screening stirs controversy
• Scientists, lawmakers target invasive Asian fish species
• Babies born by C-section more likely to become obese, study says