Over the coming days and weeks, New Horizons will continue to transmit back more images that will reveal greater detail, and closer views of the object.
Despite that primitive appearance - if not because of it - they said the object nicknamed Ultima Thule could offer profound new insight into how the planets formed more than 4½ billion years ago.
NASA originally described Ultima Thule's shape as "similar to a bowling pin" that is "spinning like a propeller", but also said it could potentially be two objects in tight orbit with one another.
It's no simple matter to reach the outer solar system, so NASA is making the most of the opportunity it has with the New Horizons probe.
So, indeed, as predicted by the mission scientists, 2014 MU69 is what's known as a contact binary.
The images released so far are "just the tip of the iceberg", Mr Stern said, adding only 1% of data stored on the spacecraft has now been received by scientists.
Another factor is that Ultima is small (about 35km in the longest dimension), and this means it doesn't have the type of "geological engine" that in larger objects will rework their composition.
Researchers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, where New Horizons is operated, were up late, working to transform those bits of data into the first high-resolution image of a Kuiper belt object.
The first color image of Ultima Thule.
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Moore said "we're basically looking at the first planetesimals", which served as building blocks for what would eventually become planets. "We are seeing a physical representation of the beginning of planetary formation, frozen in time", he said.
First, the scientists must work on the Ultima data, but they will also ask NASA to fund a further extension to the mission.
The neck area is also sloped enough that objects and fine grain elements can tumble or roll down the slopes and settle in the valley where the two lobes meet - something which likely explains the higher albedo seen in the data thus far returned from New Horizons.
Ultima Thule was once two separate space rocks that joined together, known as a contact binary.
It will take almost two years for New Horizons to beam back all of its observations of Ultima Thule.
"Everything that we're going to tell you [today] is just the tip of the iceberg", Dr Stern said. Its nearly nonexistent reflectivity didn't exactly help the New Horizons team as they sought it out.
It'll take another 20 months to download all the data from the Ultima flyby.
The hope is that the course of the spacecraft can be altered slightly to visit at least one more Kuiper belt object sometime in the next decade. "There's plenty of time to find other targets if we're in a position to having a still-healthy spacecraft, an accepted proposal, and our search is successful", Stern said.
For a half-year, the New Horizons team had puzzled over the possible shape of MU69, which was little more than an oblong dot in Hubble Space Telescope images.