Farewell Lutetia

This ethereal image shows a stunning sliver of large main-belt asteroid Lutetia from the viewpoint of ESA’s Rosetta spacecraft, taken as Rosetta passed by on its 10-year voyage towards comet 67P/Churyumov–Gerasimenko.

This week marks four years since Rosetta flew by this ancient rocky body, on 10 July 2010. As the spacecraft swung past Lutetia it snapped hundreds of high-resolution photographs with its Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS) as well as obtaining valuable spectra, and maps of the surface temperature using other instruments.

This image was taken as Rosetta had passed its closest approach, at just under 3170 km from Lutetia’s surface, and was beginning its journey away from the asteroid.

As a result of this flyby, astronomers have been able to characterise Lutetia, viewing the wide range of craters and geological features scarring the asteroid’s surface and gauging its mass and volume–and thus density and composition. These measurements showed that Lutetia is primordial, likely having formed just under 4 billion years ago during the very early phases of the Solar System.

This asteroid is one of just two that Rosetta has closely flown past, the other being asteroid Steins in 2008.

Rosetta was launched in 2004 and, after 10 years in space, will finally rendezvous with its target comet in August. It will study the comet’s surface, dust and gases in unprecedented detail, deploy a lander onto its surface, and follow the comet for over a year as it orbits around the Sun.



Amazing asteroid fly-by: Lutetia

In 2010, the ESA Rosetta satellite made a fly-by of the asteroid Lutetia. Lutetia is a remnant of the young solar system, ~100 km across, a chunk of debris cast off in a time of chaos and just-forming planets. Scientists think that it might have been a failed mini-planet, sentenced to wandering the solar system’s inner asteroid belt for the past 3.6 billion years.

Just released images have been compiled into a stunning fly-by video. Wow.

(via Rosetta Blog and Phil Plait)


Lutetia: a rare survivor from the birth of the Earth

observations indicate that the asteroid Lutetia is a leftover fragment of the same original material that formed the Earth, Venus and Mercury. Astronomers have combined data from ESA’s Rosetta spacecraft, ESO’s New Technology Telescope, and NASA telescopes. They found that the properties of the asteroid closely match those of a rare kind of meteorites found on Earth and thought to have formed in the inner parts of the Solar System. Lutetia must, at some point, have moved out to its current location in the main asteroid belt between Mars and Jupiter.

Astronomers have estimated that less than 2% of the bodies located in the region where Earth formed, ended up in the main asteroid belt. Most of the bodies of the inner Solar System disappeared after a few million years as they were incorporated into the young planets that were forming. However, some of the largest, with diameters of about 100 kilometres or more, were ejected to safer orbits further from the Sun.

Lutetia, which is about 100 kilometres across, may have been tossed out from the inner parts of the young Solar System if it passed close to one of the rocky planets and thus had its orbit dramatically altered. An encounter with the young Jupiter during its migration to its current orbit could also account for the huge change in Lutetia’s orbit.

Earlier studies of its colour and surface properties showed that Lutetia is a very unusual and rather mysterious member of the asteroid main belt. The new findings explain why Lutetia is different — it is a very rare survivor of the original material that formed the rocky planets.

Above: (1) Image of Lutetia taken by ESA’s Rosetta probe during its closest approach in July 2010. (2) Artist’s impression of Lutetia seen passing close to one of the very young rocky planets about four billion years ago and having its orbit drastically altered.

Asteroid Lutetia: postcard from the past

ESA’s Rosetta spacecraft has revealed asteroid Lutetia to be a primitive body, left over as the planets were forming in our Solar System. Results from Rosetta’s fleeting flyby also suggest that this mini-world tried to grow a metal heart.

Images from the OSIRIS camera reveal that parts of Lutetia’s surface are around 3.6 billion years old. Other parts are young by astronomical standards, at 50–80 million years old. Astronomers estimate the age of airless planets, moons, and asteroids by counting craters. The older the surface, the more impacts it will have accumulated. Some parts of Lutetia are heavily cratered, implying that it is very old.

On the other hand, the youngest areas of Lutetia are landslides, probably triggered by the vibrations from particularly jarring nearby impacts. Debris resulting from these many impacts now lies across the surface as a 1 km-thick layer of pulverised rock.

Some impacts must have been so large that they broke off whole chunks of Lutetia, gradually sculpting it into the battered wreck we see today. Astronomers don’t think Lutetia was born looking like this. It was probably round when it formed.


The asteroid Lutetia lies almost directly in the plane of the ecliptic approximately 230 million miles from the sun, on average. It was discovered in 1852 by the German-French painter, astronomer and polymath Hermann Goldschmidt, who discovered it not long after purchasing a telescope he financed by selling paintings of Galileo produced on a recent trip to Florence. Although he originally believed that he had discovered a new planet, he soon confirmed that it was indeed an asteroid and named it after the Roman name for the city that eventually became Paris: Lutetia Parisiorum, named for the Gallic tribe the Parisii who first inhabited the island later known as Île de la Cité. In July of 2010 the French spacecraft the Rosetta passed approximately 1800 miles away from Lutetia and took several hundred high resolution photographs, mostly of the north pole of the asteroid. Lutetia is a medium sized asteroid, somewhat egg shaped, 100 kilometers in diameter and 120 kilometers in diameter along its longest axis. In March 2011 the International Astronomical Union agreed to a naming system for Lutetia’s features, allowing them to be named for regions, cities and rivers in Roman Gaul: Baetica, Achaia, Etruria, Narbonensis, Noricum, Pannonia, and Raetia.

Close up image of Lutetia and image of crater cluser on Lutetia by ESA 2011 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA. Orbit of Lutetia courtesy NASA/JPL, used with permission.