Grooves on Asteroid 21 Lutetia

A portion of asteroid Lutetia, looking into the 55 km-wide Massilia crater (red circular outline) with the North Pole Crater Cluster (NPCC) in the distance (purple outline). The grooves (or ‘lineaments’) are colored according to the crater to which they are associated, i.e. red for Massilia and purple for NPCC. The blue lineaments are associated with the ‘Suspicio’ crater, while the yellow lineaments are not associated with any crater discussed in this study.

Lutetia was imaged in July 2010 by ESA’s Rosetta spacecraft, while en route to Comet 67P/Churyumov-Gerasimenko. Rosetta took images of the 100 km-wide asteroid for about two hours during the flyby. At its closest approach, Rosetta was 3162 km from Lutetia. In the image shown here, north is up.

Image credit: Besse et al (2014); image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Note: For more information, see Lutetia's Dark Side Hosts Hidden Crater.

Asteroid 21 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 characterize 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.

Image credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

The History of Different Regions on Lutetia's Surface

As ESA's Rosetta spacecraft flew past the main-belt asteroid (21) Lutetia, the OSIRIS camera on Rosetta surveyed the part of Lutetia that was visible during this period – about half of its entire surface, mostly coinciding with the asteroid's northern hemisphere. The asteroid's North Pole is indicated with a black dot.

The unique, close-up images obtained by OSIRIS have allowed scientists to identify regions characterized by very distinct geological properties with an accuracy of a few hundred meters. By tracing craters and other features on Lutetia's surface, scientists have put together a geological map for the asteroid. Their studies have shown that Lutetia's surface comprises regions spanning a wide range of ages: each of them reveals a chapter in the long and tumultuous history of this asteroid.

The most ancient portions on the surface of Lutetia are the heavily cratered Achaia and Noricum regions, shown in red and yellow in the upper and lower part of the image, respectively. With ages between 3.4 and 3.7 billion years or more, these two regions are almost as old as the asteroid itself.

Massilia, the largest crater identified on the asteroid, is located in a younger region named Narbonensis. This region is shown in blue on the right side of the image: the depression due to the large crater is clearly visible. With a diameter of 57 km, Massilia provides evidence of the most dramatic event in the history of Lutetia.

The youngest patch on the surface of Lutetia is the Baetica region, located in the vicinity of the asteroid's North Pole and shown in green at the center of the image. This region hosts a number of superimposed craters, named the North Polar Crater Cluster (NPCC), which include three large ones with sizes exceeding 10 km. These craters represent the signature left by a series of subsequent impacts that took place quite recently on geological timescales – namely, in the last few hundred million years.

Image credit: Thomas et al., (adapted from Massironi et al., ) Planetary and Space Science, Vol.66, 2012

Note: For more information, see Rosetta Flyby Uncovers the Complex History of Asteroid Lutetia.

Development of the Inner Solar System

This artist’s impression shows four stages of the development of the inner Solar System over a period of nearly five billion years. The top panel shows the earliest stage where the debris disc around the Sun was composed of gas and tiny particles, typically less than one millimeter across. At the second stage the particles have formed large clumps, roughly 100 kilometers across and, similar to the asteroid Lutetia. These bodies in turn formed the rocky planets including the Earth, shown in the third panel down. Over the subsequent four billion years the surface of the Earth developed to what we know now under the influence of meteor bombardment that delivered volatile materials including water, and the evolution of life on its surface.

The rare spectral properties show that Lutetia started life as a fragment of the material that was forming the inner planets but was ejected. It is now found as an unusual interloper in the main belt of asteroids, much further from the Sun.

Illustration credit: ESO/L. Calçada and N. Risinger

Note: For more information, see Lutetia: a Rare Survivor from the Birth of the Earth.

Landslides and Boulders on Asteroid 21 Lutetia

This close-up view of a crater in the Baetica region on asteroid (21) Lutetia shows boulders and landslides.

Several hundred boulders up to 300 meters across have been identified - these are among the largest rocks found so far on small bodies in the Solar System.

Landslides on Lutetia are thought to have been caused by the vibrations created by impacts elsewhere on the asteroid dislodging pulverized rocks.

This image was obtained by the OSIRIS imaging system on Rosetta during the 10 July 2010 flyby of asteroid (21) Lutetia.

Photo credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

Note: For more information about the scientific analysis of Asteroid 21 Lutetia, see Rosetta Reveals Mysterious Lutetia.

Asteroid Lutetia

Asteroid Lutetia has been revealed as a battered world of many craters. ESA’s Rosetta mission has returned the first close-up images of the asteroid showing it is most probably a primitive survivor from the violent birth of the Solar System.

The flyby was a spectacular success with Rosetta performing faultlessly. Closest approach took place at 18:10 CEST [July 10], at a distance of 3,162 km.

The images show that Lutetia is heavily cratered, having suffered many impacts during its 4.5 billion years of existence. As Rosetta drew close, a giant bowl-shaped depression stretching across much of the asteroid rotated into view. The images confirm that Lutetia is an elongated body, with its longest side around 130 km.

The pictures come from Rosetta’s OSIRIS instrument, which combines a wide angle and a narrow angle camera. At closest approach, details down to a scale of 60 m can be seen over the entire surface of Lutetia.

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Rosetta operated a full suite of sensors at the encounter, including remote sensing and in-situ measurements. Some of the payload of its Philae lander were also switched on. Together they looked for evidence of a highly tenuous atmosphere, magnetic effects, and studied the surface composition as well as the asteroid’s density.

They also attempted to catch any dust grains that may have been floating in space near the asteroid for on-board analysis. The results from these instruments will come in time.

The flyby marks the attainment of one of Rosetta’s main scientific objectives. The spacecraft will now continue to a 2014 rendezvous with its primary target, Comet Churyumov-Gerasimenko. It will then accompany the comet for months, from near the orbit of Jupiter down to its closest approach to the Sun. In November 2014, Rosetta will release Philae to land on the comet nucleus.

Photo credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

Note: For more information and photographs, see Rosetta Triumphs at Asteroid Lutetia

Update: The website Space.com has an interesting article about Asteroid Lutetia: Peek at Huge Asteroid Provides More Questions Than Answers