Solar System

We just can't get our solar system right. First, the beloved Pluto is downgraded to "dwarf planet. " Now it turns out that the moon may be 200 million years younger than scientists estimated. A study in the journal Nature, based on a new analysis of a lunar rock brought back to Earth in 1972 by Apollo 16 astronauts, indicates that the moon could be a more youthful 4.36 billion years old — and that the process by which it was formed happened later than scientists thought. Or possibly this lunar rock, part of the moon's crust, isn't exactly what scientists thought it was. Maybe the crust wasn't formed by a magma ocean after all. "And that's a big deal," said Lars Borg, the lead author of the study and a geochemist at Lawrence Livermore National Laboratory.

NASA's spacecraft Juno lifted off Friday in an incandescent arc over the Atlantic Ocean, the start of a five-year, 1.7-billion mile trip to Jupiter that scientists believe will unlock some of the secrets behind the origin of the solar system. NASA's spacecraft Juno lifted off Friday in an incandescent arc over the Atlantic Ocean, the start of a five-year, 1.7-billion mile trip to Jupiter that scientists believe will unlock some of the secrets behind the origin of the solar system.

Turns out the moon's not the Earth's only traveling companion. Space scientists have discovered an asteroid that's been following our fair planet for thousands of years, at least — and there may be many more where it came from, according to a recent study. If other so-called Trojan asteroids are found, they could turn out to be ideal candidates for a visit from astronauts, something NASA hopes will be possible within the next 15 years. Most of the asteroids in the solar system populate the belt of rocky debris between Mars and Jupiter.

Even for scientists versed in the grand scale of astronomy, it's never been easy to grasp the scope of Jupiter. After all, you could fit every piece of the solar system other than the sun inside Jupiter — all the other planets, moons and asteroids — with plenty of room to spare. Jupiter has cannibalized 20 moons over the years and still has at least 63, one bigger than Mercury. Jupiter's "spot" is actually a hurricane, which has lasted for hundreds of years and is more than twice the diameter of Earth.

We've brought back dust from a comet; now NASA plans to do the same for an asteroid. The Osiris-Rex mission will launch in 2016 and head to the near-Earth asteroid known as 1999 RQ36, where it will circle for about a year before swooping down and using a robotic arm to scoop up cupfuls of material, which it will bring back for scientists to study. Asteroids are leftovers from the formation of the solar system 4.5 billion years ago. Having a bit of them to study would be like getting a glimpse into what the early solar system looked like as the disc of debris around the sun began to coalesce into planets, asteroids and other bodies.

The 2004 crash-landing of a returning NASA space capsule in the deserts of Utah had scientists fearing for a while that samples collected by the Genesis mission, sent to capture particles from the sun's solar wind, were lost. But much of the collected material survived the crash, and it's now turning up surprises: discrepancies between the composition of the sun and the inner solar system, which contains the sun's four closest planets, including Earth. The early report, published online Monday in the journal Proceedings of the National Academy of Sciences, shows among other things that the pattern of isotopes in the solar wind — and thus, presumably, the sun — is very different from that of the inner planets.

SolarCity, the Bay Area company that is the leading provider of residential solar systems, shook up the renewable energy industry by pioneering a financing program that made solar panels accessible to more than rich eco-fans. The company ? founded in 2006 by brothers Lyndon and Peter Rive ? has completed or is working on more than 10,000 solar projects and is expanding to the East Coast. The company has ballooned to more than 1,000 employees, even though progress was stalled during the recession, and it has raised more than $700 million in project financing.

Look, Pluto had a good run. While 76 years is nothing in astronomical time, in the human span it's a whole lifetime. For all those decades, Pluto was regarded as a planet, the smallest and most distant member of our solar system family. It had an affectionate place in human hearts, and a Disney cartoon character and an element as famous namesakes. And then, Mike Brown killed it. He admits as much; it's the title of his book, "How I Killed Pluto and Why It Had It Coming. " In 2005, the Caltech astronomer found, in the same neighborhood as Pluto, an object at least as big as Pluto, which he called Eris.