Researchers have received the best picture yet of the small, icy object Ultima Thule, which it flew past on New Year's Day.
The image was acquired when the NASA's New Horizons spacecraft was just 6,700km from its target, which scientists think is two bodies lightly fused together - giving the look of a snowman.
The rendezvous between the New Horizons probe and the distant object known as Ultima Thule was an historic moment, but after the mind-blowing imagery the craft sent back from Pluto, you could be forgiven for being a little disappointed in how indistinct the early imagery was. Those concerns should be partly alleviated by the latest image from the probe, which shows the rocky world in considerably greater detail.
Surface details are now much clearer. It’s still not exactly poster quality, but remember, this is being beamed back bit by bit from four billion miles away. And it isn’t just sending the best stuff, but a huge series of images it took during the brief flyby on January 1. Not only that, but there are multiple imagers and instruments whose information must be collated and adjusted for human viewing.
It's going to take fully 20 months to pull all the pictures and other scientific observations from the spacecraft, even though all this information was gathered over just a couple of days during the course of the flyby.
Obtained with the wide-angle Multicolour Visible Imaging Camera (MVIC) component of New Horizons’ Ralph instrument, this image was taken when the KBO was 6,700 kilometres (4,200 miles) from the spacecraft on 1 January. With an original resolution of 135 metres (440 feet) per pixel, the image was stored in the spacecraft’s data memory and transmitted to Earth on 18-19 January. Scientists then sharpened the image to enhance fine detail. (This process – known as deconvolution – also amplifies the graininess of the image when viewed at high contrast.)
An artist’s impression of the Ultima Thule flyby. Image credit: NASA/JHUAPL/SwRI
The lighting is fortuitous, and helps show off the topography of Ultima Thule, or 2014 MU69, as it was previously known. To give you a sense of scale, the big concavity in what you might call the head of the snowman is about 4 miles across.
Ultima Thule's topography has now sharpened sufficiently for us to see the defined outline of a number of pits, especially along the day/night boundary, or terminator.
Both lobes also show many intriguing light and dark patterns of unknown origin, which may reveal clues about how this body was assembled during the formation of the Solar System 4.5 billion years ago. One of the most striking of these is the bright “collar” separating the two lobes.
Researchers will have to determine whether the pits are impact craters or voids created by some other type of process - such as the escape of volatile materials.
Ultima Thule, a conglomeration of ice and dust, orbits the Sun in a sparsely populated and low-energy environment known as the Kuiper belt.
The chance of a collision with other objects ought therefore to be exceedingly low, but then this snowman was very probably created right at the start of Solar System formation and has had time to pick up at least a few scars.