Dawn Spacecraft Begins Approach to Dwarf Planet Ceres

• Dawn has entered its approach phase toward Ceres
• The spacecraft will arrive at Ceres on March 6, 2015

NASA's Dawn spacecraft has entered an approach phase in which it will continue to close in on Ceres, a Texas-sized dwarf planet never before visited by a spacecraft. Dawn launched in 2007 and is scheduled to enter Ceres orbit in March 2015.
Dawn recently emerged from solar conjunction, in which the spacecraft is on the opposite side of the sun, limiting communication with antennas on Earth. Now that Dawn can reliably communicate with Earth again, mission controllers have programmed the maneuvers necessary for the next stage of the rendezvous, which they label the Ceres approach phase. Dawn is currently 400,000 miles (640,000 kilometers) from Ceres, approaching it at around 450 miles per hour (725 kilometers per hour).
The spacecraft's arrival at Ceres will mark the first time that a spacecraft has ever orbited two solar system targets. Dawn previously explored the protoplanet Vesta for 14 months, from 2011 to 2012, capturing detailed images and data about that body.
"Ceres is almost a complete mystery to us," said Christopher Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. "Ceres, unlike Vesta, has no meteorites linked to it to help reveal its secrets. All we can predict with confidence is that we will be surprised."
The two planetary bodies are thought to be different in a few important ways. Ceres may have formed later than Vesta, and with a cooler interior. Current evidence suggests that Vesta only retained a small amount of water because it formed earlier, when radioactive material was more abundant, which would have produced more heat. Ceres, in contrast, has a thick ice mantle and may even have an ocean beneath its icy crust.
Ceres, with an average diameter of 590 miles (950 kilometers), is also the largest body in the asteroid belt, the strip of solar system real estate between Mars and Jupiter. By comparison, Vesta has an average diameter of 326 miles (525 kilometers), and is the second most massive body in the belt.
The spacecraft uses ion propulsion to traverse space far more efficiently than if it used chemical propulsion. In an ion propulsion engine, an electrical charge is applied to xenon gas, and charged metal grids accelerate the xenon particles out of the thruster. These particles push back on the thruster as they exit, creating a reaction force that propels the spacecraft. Dawn has now completed five years of accumulated thrust time, far more than any other spacecraft.
"Orbiting both Vesta and Ceres would be truly impossible with conventional propulsion. Thanks to ion propulsion, we're about to make history as the first spaceship ever to orbit two unexplored alien worlds," said Marc Rayman, Dawn's chief engineer and mission director, based at NASA's Jet Propulsion Laboratory in Pasadena, California.
The next couple of months promise continually improving views of Ceres, prior to Dawn's arrival. By the end of January, the spacecraft's images and other data will be the best ever taken of the dwarf planet.
The Dawn mission to Vesta and Ceres is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington. UCLA is responsible for overall Dawn mission science.

The space station orbits onward

it may not sound like the most dramatic news. But as Charles Fishman points out in an outstanding new feature in the Atlantic, the International Space Station has now been occupied for nearly 5,200 days since its 2009 completion. We don't pay it much attention, but as he writes, "in the past decade, America has become a truly, permanently spacefaring nation."

The ISS hasn't produced any huge scientific discoveries or technologies — mainly, it's an exercise in figuring out how humans can adapt to living in space. In March, astronaut Scott Kelly will head to the ISS for NASA's first ever year-long mission, twice as long as most astronauts spend in orbit. The surreal sunrise timelapse above, captured by the European Space Agency's Alexander Gerst, shows what astronauts spend much of their time on the ISS staring at: the Earth, spinning swiftly underneath them day and night.

Curiosity keeps finding evidence that Mars was once habitable

Layers of sedimentary rock in Gale Crater photographed by Curiosity, which serve as evidence of an ancient lakebed. (NASA/JPL-Caltech/MSSS)

In 2014, the Curiosity probe's big Mars discoveries kept coming. Most recently, in December, it discovered evidence of an ancient lakebed, as well as organic molecules and mysterious plumes of methane gas. Together, these findings and other data have many scientists convinced that Mars was once warmer and wetter than it is today — and perhaps even home to life.
In 2015, the rover will climb a giant mountain called Mount Sharp, sampling a succession of rock layers that will help us learn more about the planet's geologic and atmospheric history.

NASA tests its Orion capsule for the first time

The Orion capsule, after its December 2014 test flight. (U.S. Navy via Getty Images)

In December, NASA carried out a successful test of its Orion capsule — a spacecraft that it hopes to use to carry astronauts into deep space. Plans are still uncertain, but NASA's stated goal for Orion is to eventually use it to put humans on Mars.
This first test, with an uncrewed capsule, was a success, with the craft making two orbits of the Earth, including one at an altitude of 3,600 miles. This is more than ten times higher up than the International Space Station, and farther away from Earth than any crewable craft has traveled since 1972.

Philae touches down on the comet 67P/C-G

In November, the European Space Agency's Philae because the first spacecraft ever to land on a comet. the photos was taken by Philae upon landing.
The landing didn't go exactly as planned — the lander actually took a series of large bounces because its harpoons didn't fire upon landing — but the mission was still a huge success. Data from both Philae and Rosetta (the spacecraft that brought it to the comet and is still orbiting it) have already provided new information about comets, which could help us better understand the formation of the solar system.

Virgin Galactic's SpaceShipTwo crashes over California

Wreckage from the SpaceShipTwo crash. (Sandy Huffaker/Getty Images)

In October, Virgin Galactic's SpaceShipTwo — a space plane that the company intends to use to carry tourists into low Earth orbit — crashed during a test flight in California, killing one pilot. The accident came just days after another private spaceflight disaster: the explosion of an uncrewed rocket, owned by the Orbital Sciences Corporation, which was heading to the International Space Station for a cargo resupply mission.
The cause of the Virgin accident still hasn't been fully determined, but it comes after experts had previously criticized the company's cavalier attitude towards safety. Still, Virgin says it will proceed with its plans to carry tourists into space.

The most detailed map yet of our place in the universe

An illustration of the Laniakea supercluster, home to the Milky Way and hundreds of thousands of other galaxies. (Nature)

In September, scientists released a truly awe-inspiring map: one that shows our galaxy's place among hundreds of thousands of others, as part of a giant supercluster of galaxies called Laniakea.

The enormous structure is an estimated 500 million light years across, and is home to more than 100,000 galaxies. Each of these galaxies, meanwhile, contains billions or perhaps even trillions of stars. And our supercluster, the scientists found, borders another, similarly large one called Perseus-Pisces.