Rosetta Discovers Haunting Beauty in Deep Space


July 14, 2010:  The European Space Agency's Rosetta spacecraft has beamed back close-up photographs of asteroid Lutetia, an ancient, cratered relic from the dawn of the solar system. Scientists are abuzz about the stunning images, which reveal a worldlet of haunting, alien beauty.

"I've never seen anything like it," says Claudia Alexander, project scientist for the U.S. Rosetta Project. "It looked as though it could have been fractured off of a mother asteroid – it was all angles and flat planes, ancient impacts overlaid by newer ones, covered by dust of some kind."

Asteroid Lutetia (Alfred Hitchcock, 550px)
Some observers are calling this the "Alfred Hitchcock" shot. Rosetta took the picture as it was receding from Lutetia on July 10th. Credit: ESA [larger image]

She is particularly intrigued by a giant dent in the asteroid's side.

"My first guess would be that it's the remnant of a giant collision that occurred sometime in the distant past," says Alexander. "The edges look shallow rather than sharp and deep as might be the case with a fresh crater. I'm sure there will be much more analysis of that feature in the weeks to come."

And then there's the perplexing appearance that boulders rolled down Lutetian slopes at some point.

"If that is indeed what we're seeing, the question becomes 'what could have caused the rolling? Perhaps the asteroid spun-up, spun-down, or experienced some orbital irregularity. It's not clear right now that the asteroid is subject to the forces that could cause these things. This is another issue for further study."

Asteroid Lutetia (landslide, 550px)
A possible landslide and boulders on asteroid Lutetia. Credit ESA. [larger image]

"Right now we have more questions than answers," Alexander continues. "We can only speculate at this point about what we're seeing in the pictures."

Asteroid Lutetia has been a target of interest among astronomers for many years. It is one of the largest asteroids in the solar system and has a strange spectrum of reflected light that doesn't look quite like any other asteroid. When the opportunity presented itself for Rosetta to pay a visit en route to its prime target, comet 67P/Churyumov-Gerasimenko in 2014, mission planners couldn't pass it up.

Now that Alexander has seen the images, she can't help but wonder what it would be like to have a walk around.

Asteroid Lutetia (conjunction, 200px)
Lutetia and Saturn. Credit: ESA [larger image]

"Astronauts would have a hard time walking on Lutetia -- the gravity is likely to be much less than that of the moon," she says. "Also, the surface regolith looks very powdery, so astronauts might find themselves sinking in maybe a half-inch or so as they walked."

NASA's MIRO (Microwave Instrument for the Rosetta Orbiter) instrument will help determine whether the surface layers are powdery or rocky. As scientists analyze data from Rosetta's other instruments, they'll be able to determine Lutetia's mass and density, thus revealing more about the asteroid's composition and helping solve the riddle of its origin.

Is Lutetia a 130-km fragment from a planet that broke apart billions of years ago? Or is it one of the original planetary building blocks astronomers call "planetesimals" that has remained the same because no planet sucked it in during the solar system's formative years?

As scientists begin to answer these questions with the Rosetta data, they'll gain new insights into the origin and history of asteroids, and also learn more about the evolution of the solar system itself. An asteroid's contents can reveal something about the conditions and makeup of the solar nebula where the asteroid formed.

"Rosetta took measurements with 17 different instruments," says Rita Schulz, ESA Project Scientist for the Rosetta Mission. "When all the data are analyzed, Lutetia will be one of the best known asteroids out there."

"These spectacular images," she says, "are just the beginning."

Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA


Mysterious Asteroid Unmasked By Space Probe Flyby
By Denise Chow Staff Writer
posted:2010 July 10
02:53 pm ET

A European spacecraft zoomed by past a mysterious asteroid Saturday July 10  to take the first-ever close look at the space rock while flying more than 282 million miles from Earth.

The European Space Agency's (ESA) Rosetta space probe flew past the asteroid Lutetia, an object discovered in 1852 that appeared only as a bright speck in the sky to astronomers until today.

The first new photos of the asteroid  (SHOWN BELOW) revealed Lutetia to be a lumpy rock with a potato-like appearance. Rosetta was about 1,900 miles (3,100 km) from the asteroid at its closest approach.

  • OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System). The camera system consisting of a narrow angle (700 mm) and a wide angle camera (140 mm), with an 2048x2048 pixel CCD chip each will take pictures of the comets. The instrument was constructed in Germany.[14]

The enigmatic space rock, which is about 62 miles (100 km) wide, is from the main asteroid belt that orbits between Mars and Jupiter. From Earth, Lutetia simply appears as little more than a single point of light to ground-based telescopes.

As a result, not much was known about Lutetia, including what it looks like. Data from Rosetta's encounter could provide more conclusive evidence about the asteroid's dimensions and composition. [More asteroid photos.]

"We know approximately its size and rotational period," Rosetta project scientist Rita Schulz said in a live webcast during the probe's flyby. "The rotational period is something like eight hours, and that will be confirmed after the flyby. We are now going to get the details. What is very important for us is the composition of the asteroid."

The asteroid flyby was actually a pit stop for Rosetta, which continued on toward its main target – comet 67P/Churyumov-Gerasimenko

The spacecraft launched in 2004 and is expected to arrive at the comet in 2014. Rosetta also visited a different space rock, the asteroid Steins, in 2008.

Asteroid Blind Date

Saturday's asteroid flyby was watched over by dedicated team of mission scientists at the ESA Space Operations Center in Darmstadt, Germany. The rendezvous was webcast live on ESA's website.

At 1514 GMT (11:15 a.m. EDT), Rosetta Spacecraft Operations Manager Andrea Accomazzo confirmed that the probe had entered autonomous tracking mode in preparation for the flyby. The navigation camera was used to keep the spacecraft pointed at Lutetia.

The closest encounter occurred at approximately 1610 GMT (12:10 p.m. EDT), with Rosetta traveling at a relative speed of 32,400 mph (52,142 kph).

ESA scientists were able to track Rosetta up to five minutes to closest approach, after which the radio signal with the probe was lost as the spacecraft turns its antenna away from Earth and faces the asteroid instead.

After approximately 40 minutes, a series of maneuvers restored the antenna's Earth lock, and the probe began successfully transmitting data and telemetry back to its ground controllers once again.  

ESA scientists hope the observations from the Lutetia flyby will contribute to the relatively small body of knowledge about asteroids.

Unmasking Asteroid 21 Lutetia

The close pass allowed Rosetta about two hours of observation time to scrutinize the asteroid Lutetia.

Rosetta will continue beaming this data to Earth, and the first close-up pictures from the quick visit are expected to be released later tonight. Preliminary images from ESA were released in the lead up to the encounter, showing Lutetia looming larger and larger as Rosetta approached within about 49,700 miles (80,000 km).

The data collected from Rosetta's visit will provide valuable observations for asteroid science, and will at least give scientists preliminary information that can then be corroborated through ground-based observations. And, the findings will not only apply for Lutetia, but for other asteroids as well.

Rosetta is a European Space Agency- led robotic spacecraft mission launched in 2004, intended to study the comet 67P/Churyumov-Gerasimenko. It is intended to orbit the comet and place a lander upon it, in 2014. Rosetta consists of two main elements: the Rosetta space probe and the Philae lander. The spacecraft will also fly by and examine two asteroids ( 2867Steins & 21 Lutetia) on its way to the comet.[1]

The probe is named after the Rosetta Stone, as it is hoped the mission will help unlock the secrets of how our solar system looked before planets formed. The lander is named after the Nile island Philae where an obelisk was found that helped decipher the Rosetta Stone.

The craft completed its third Earth fly-by in late 2009, and is presently functioning and on-target for its final destination.

Operator European Space Agency
Major contractors European Space Agency
Mission type Comet Orbiter/Lander
Flyby of Earth, Mars, 2867 Šteins, 21 Lutetia
Satellite of 67P/Churyumov-Gerasimenko
Launch date March 2, 2004 at 07:17 UTC
Launch vehicle Ariane 5G+
Mission duration 6 years, 3 months, and 12 days elapsed
Orbital decay N/A
COSPAR ID 2004-006A
Homepage ESA-Rosetta



  Mission Timeline

This is the planned timeline for the mission after its launch:

  • First Earth flyby (March 4, 2005)
  • Mars flyby (February 25, 2007)
  • Second Earth flyby (November 13, 2007 )
  • Flyby of asteroid 2867 Šteins (September 5, 2008)
  • Third Earth flyby (November 13, 2009)
  • Flyby of asteroid 21 Lutetia  (July 10, 2010) - JUST OCCURRED - See the Article on 21 Lutetia BELOW the Rosetta article

  • Deep-space hibernation (May 2011 - January 2014)
  • Comet approach (January-May 2014)
  • Comet mapping / Characterization (August 2014)
  • Landing on the comet (November 2014)
  • Escorting the comet around the Sun (November 2014 - December 2015)

Where is Rosetta now :


During the 1986 apparition of the Comet Halley, a number of international space probes were sent to explore the cometary system, most prominent among them being ESA's highly successful Giotto. After the probes returned a treasure-trove of valuable scientific information it was becoming obvious that follow-ons were needed that would shed more light on the complex cometary composition and resolve the newly opened questions.

Both NASA and ESA started cooperatively developing new probes. The NASA project was the Comet Rendezvous Asteroid Flyby or CRAF mission. The ESA project was the follow-on Comet Nucleus Sample Return (CNSR) mission. Both missions were to share the Mariner Mark II spacecraft design, thus minimizing costs. In 1992, after NASA axed CRAF due to budgetary limitations, ESA decided to develop a CRAF-style project on its own. By 1993 it was evident that the ambitious sample return mission was unfeasible with the existing ESA budget, so the mission was redesigned, with the final flight plan resembling the canceled CRAF mission, an asteroid flyby followed by a comet rendezvous with in-situ examination, including a lander.

Rosetta was built in a clean room according to COSPAR rules, but "Sterilisation [was] generally not crucial since comets are usually regarded as objects where you can find prebiotic molecules, that is, molecules that are precursors of life, but not living microorganisms,"[2] according to Gerhard Schwehm, Rosetta's Project Scientist.

It was set to be launched on January 12, 2003 to rendezvous with the comet 46P/Wirtanen in 2011.

Trajectory of the Rosetta Space Probe

However, this plan was abandoned after a failure of the planned launch vehicle Ariane 5 on December 11, 2002. A new plan was formed to target the comet Churyumov-Gerasimenko, with launch on February 26, 2004 and rendezvous in 2014. The larger mass and the resulting increased impact velocity made modification of the landing gear necessary.[3] After two cancelled launch attempts, Rosetta was launched on March 2, 2004 at 7:17 GMT. Besides the changes made to launch time and target, the mission profile remains almost identical.

The first flyby of Earth occurred on March 4, 2005.

On February 25, 2007, the craft was scheduled for a low-altitude bypass of Mars, to correct the trajectory after the first launch in 2003 was delayed by one year. This was not without risk, as the estimated altitude of the flyover manoeuvre was a mere 250 km (155 miles). During that encounter the solar panels could not be used since the craft was in the planet's shadow, where it would not receive any solar light for 15 minutes, causing a dangerous shortage of power. The craft was therefore put into standby mode, with no possibility to communicate, flying on batteries that were originally not designed for this task.[4] This Mars manœuvre was therefore nicknamed "The Billion Dollar Gamble".[5] Fortunately, the flyby was successful and the mission now continues.[6]

The second Earth flyby occurred on November 13, 2007.[7][8]

The spacecraft performed a close flyby of asteroid 2867 Šteins on September 5, 2008. Its onboard cameras were used to fine-tune the trajectory, achieving a minimum separation of less than 800 km (497 miles). Onboard instruments measured the asteroid from August 4 to September 10. Maximum relative speed between the 2 objects during the flyby was 8.6 km/s (19,240 mph).[9]

Rosetta's third and final flyby of Earth happened on November 12, 2009.[10]

The asteroid's orbit was known before Rosetta's launch, from ground-based measurements, to an accuracy of approximately 100 km. Information gathered by the onboard cameras beginning at a distance of 24 million km will be processed at ESA's Operation Center to refine the asteroid's position in its orbit to a few km.

In May 2014, the Rosetta craft will enter a slow orbit around the comet and gradually slow down in preparation for releasing a lander that will make contact with the comet itself. The lander, named "Philae", will approach Churyumov-Gerasimenko at relative speed around 1 m/s and on contact with the surface, two harpoons will be fired into the comet to prevent the lander from bouncing off. Additional drills are used to further secure the lander on the comet.

Once attached to the comet, expected to take place in November 2014, the lander will begin its science mission:

  • Characterisation of the nucleus
  • Determination of the chemical compounds present, including enantiomers[11]
  • Study of comet activities and developments over time

The exact surface layout of the comet is currently unknown and the orbiter has been built to map this before detaching the lander. It is anticipated that a suitable landing site can be found, although few specific details exist regarding the surface.

Computer model of Rosetta probe



The spectroscopical investigation of the core is done by four instruments:

  • ALICE (an ultraviolet imaging spectrograph). The UV spectrograph will search for the abundance of noble gas in the comet core, from which the temperature during the comet creation could be estimated. The detection is done by an array of potassium bromide and caesium iodide photocathodes. The 3.1 kg instrument uses 2.9 watts and was produced in the USA, and an improved version is used in the New Horizons.[12][13]
  • OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System). The camera system consisting of a narrow angle (700 mm) and a wide angle camera (140 mm), with an 2048x2048 pixel CCD chip each will take pictures of the comets. The instrument was constructed in Germany.[14]
  • VIRTIS (Visible and Infrared Thermal Imaging Spectrometer). The Visible and IR spectrometer is able to make pictures of the core in the IR and also search for IR spectra of molecules in the coma. The detection is done by a mercury cadmium teluride array for IR and with a CCD chip for the Visible range. The instrument was produced in Italy, and improved versions were used for Dawn and Venus express.[15]
  • MIRO (Microwave Instrument for the Rosetta Orbiter). With the microwave emissions the temperature and the abundance of volatile substances (like water, ammonia and carbon dioxide) can be detected. The 30 cm radio antenna was constructed in Germany, while the rest of the 18.5 kg instrument was provided by the USA.

The radar tomography of the nucleus is performed by:

  • CONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission). The CONSERT experiment is the only experiment on board the ROSETTA mission which will provide information about the deep interior of the comet. The Consert radar will perform the tomography of the nucleus by measuring electromagnetic wave propagation from the Philae lander and the Rosetta orbiter throughout the comet nucleus in order to determine its internal structures and to deduce information on its composition. The lander and orbiter electronics was provided by France and both antennas were constructed in Germany.[16]

  Gas and Particles

  • ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis). The instrument consists a double focus magnetic mass spectrometer DFMS and a reflectron type time of flight mass spectrometer RTOF. The DFMS has a high resolution (can resolve N2 from CO) for molecules up to 300 amu. The RTOF is highly sensitive for neutral molecules and for ions.[17]
  • MIDAS (Micro-Imaging Dust Analysis System). The high resolution atomic force microscope will investigate the dust particles which are deposited on a silicone plate.[18]
  • COSIMA (Cometary Secondary Ion Mass Analyser). Composition of dust particles is analysed, after the surface is cleaned by indium ions, by secondary ion mass spectrometry. Ions up to a mass of 4000 amu is possible.[19]

  Solarwind Interaction

  • GIADA (Grain Impact Analyser and Dust Accumulator) [20]
  • RPC (Rosetta Plasma Consortium).[21][22]

  Major Events and Discoveries


  • March 2 – ESA's Rosetta mission is successfully launched at 07:17 GMT (08:17 Central European Time). The launcher successfully placed its upper stage and payload into an eccentric coast orbit (200 x 4,000 km). About two hours later, at 09:14 GMT, the upper stage ignited its own engine to reach an escape velocity in order to leave the Earth’s gravity field and enter heliocentric orbit. The Rosetta probe was released 18 minutes later. ESA’s Operations Centre (ESOC) in Darmstadt, Germany, established contact with the probe shortly after that.
  • May 10 – The first and most important deep space maneuver was successfully executed and brings the space craft on its correct course, with a reported inaccuracy of 0.05%.


  • March 4 – Rosetta executed its first planned close flyby of Earth. The Moon and the Earth's magnetic field were used to test and calibrate the instruments on board of the spacecraft. The minimum altitude above the Earth's surface was about 1,954.7 km at 22:09 UTC and images of the space probe passing by were captured by amateur astronomers.[23]
  • July 4 – Imaging instruments on board observed the collision between the comet Tempel 1 and the impactor of the Deep Impact mission.[24]


  • February 25 – Mars swing-by. Philae's ROMAP (Rosetta Lander Magnetometer and Plasma Monitor) instrument measures the complex Martian magnetic environment,[25] while Rosetta's OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) took various images of the planet using different photographic filters.[26] While in Mars' shadow most of the instruments were turned off the Philae lander was autonomously running on batteries. During this operation the ÇIVA instrument on the lander took pictures of Mars.[27][28] Among others, both actions were meant to test the spacecraft's instruments while the probe needed the gravity of Mars to change directions in order to undertake its second Earth flyby in November.[29]
  • November 8 – As Rosetta approached the Earth for its second flyby scheduled for November 13, it was observed by a 0.68 meter telescope of the Catalina Sky Survey near Tucson, Arizona as a moving object on survey images from November 7 and its positions were reported to the Minor Planet Center. After additional observations on November 8 the Minor Planet Center misidentified the spacecraft as a Near Earth Object on a course that would bring it within 0.89 earth radii from the surface of the Earth and gave it the provisional designation asteroid 2007 VN84. Following a suggestion on a news group, the misidentification was corrected and the asteroid designation was cancelled one hour and 16 minutes later.[30]



  • November 13 – Last swingby (gravity assist passage) of Earth. The spacecraft is scheduled to make its closest approach (perigee passage) at 2481 km altitude over 109°E and 8°S - just off the coast of the Indonesian island of Java, at 08:45 CET (07:45 UT).[32]

  Misidentification as an Asteroid

In November, 2007, the Rosetta spacecraft was mistaken for a dangerous near-Earth asteroid and given the designation 2007 VN84. An astronomer 'discovered' the spacecraft and misidentified it as an asteroid about 20 meters in diameter, and performed a trajectory calculation showing that it would make its closest flyby of the Earth at a distance of 5,700 kilometers on November 13, 2007. This extremely close approach (in astronomical terms) led to speculation that 2007 VN84 might be at risk of impacting the Earth.[33] However, astronomer Denis Denisenko recognized that the trajectory matched that of the Rosetta probe, which was performing a flyby of Earth en route to its rendezvous with a comet.[34] The Minor Planet Center later confirmed in an editorial release[35] that 2007 VN84 was actually the spacecraft.


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Categories: European Space Agency | European Space Agency probes | Comet/Asteroid missions | Space exploration | 2004 in space exploration | Mars missions | Active extraterrestrial probes | Spaceflights | 2004 in spaceflight


21 Lutetia is a large main belt asteroid. It is an unusual form of M-type asteroid about 100 kilometers in diameter. The name

Lutetia derives from the Latin name for Paris. Lutetia will be the object of a flyby by the Rosetta space probe on 2010 July 10.



  Discovery and Exploration

Lutetia was discovered on November 15, 1852 by Hermann Goldschmidt from the balcony of his apartment in Paris.[7]

There have been two reported stellar occultations by Lutetia, observed from Malta in 1997 and Australia in 2003, with only one chord each, roughly agreeing with IRAS measurements.[citation needed]

On July 10, 2010, the European Rosetta space probe will pass Lutetia at a minimum distance of 3160 km and a velocity of 15 kilometres per second on its way to the comet 67P/Churyumov-Gerasimenko.[8] Lutetia will be the first M-type asteroid to be visited by a spacecraft.


The composition of Lutetia has puzzled astronomers for some time, and investigation has picked up in recent years in anticipation of the upcoming Rosetta flyby. While classified among the M-type asteroids, most of which are metallic, Lutetia is one of the anomalous members that do not display much evidence of metal on their surface. Indeed, there are various indications of a non-metallic surface: a flat, low frequency spectrum similar to that of carbonaceous chondrites and C-type asteroids and not at all like that of metallic meteorites,[9] a low radar albedo unlike the high albedos of strongly metallic asteroids like 16 Psyche,[6] evidence of hydrated materials on its surface,[10] abundant silicates,[11] and a thicker regolith than most asteroids.[12]

Lightcurve analysis indicates that Lutetia is a rough sphere with "sharp and irregular shape features" and that its pole points toward either ecliptic coordinates (β, λ) = (3°, 40°) or (β, λ) = (3°, 220°) with a 10° uncertainty.[4] This gives an axial tilt of 85°, or 89°, respectively, meaning that Lutetia spins at an approximately right angle to the ecliptic, like the planet Uranus.


  1. ^ a b c d "JPL Small-Body Database Browser: 21 Lutetia". 2008-09-25 last obs. Retrieved 2008-12-07. 
  2. ^ a b c Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. Retrieved 2008-11-28. 
  3. ^ Supplemental IRAS Minor Planet Survey
  4. ^ a b J. Torppa et al. (2003). "Shapes and rotational properties of thirty asteroids from photometric data" (PDF). Icarus 164: 346. doi:10.1016/S0019-1035(03)00146-5. 
  5. ^ a b M. Mueller et al. (2006). "The size and albedo of Rosetta fly-by target 21 Lutetia from new IRTF measurements and thermal modeling". Astronomy & Astrophysics 447: 1153. doi:10.1051/0004-6361:20053742. 
  6. ^ a b C. Magri et al. (1999). "Mainbelt Asteroids: Results of Arecibo and Goldstone Radar Observations of 37 Objects during 1980-1995". Icarus 140: 379. doi:10.1006/icar.1999.6130. 
  7. ^ Lardner, Dionysius (1867). "The Planetoides". Handbook of astronomy. James Walton. p. 222. 
  8. ^ M. A. Barucci, M. Fulchignoni and A. Rossi (2007). "Rosetta Asteroid Targets: 2867 Šteins and 21 Lutetia". Space Science Reviews 128 (1-4): 67–78. doi:10.1007/s11214-006-9029-6. 
  9. ^ Birlan, M., et al. (2004). "Near-IR spectroscopy of asteroids 21 Lutetia, 89 Julia, 140 Siwa, 2181 Fogelin and 5480 (1989YK8) [sic], potential targets for the Rosetta mission; remote observations campaign on IRTF". New Astronomy 9: 343. doi:10.1016/j.newast.2003.12.005. 
  10. ^ M. Lazzarin et al. (2004). "Visible spectral properties of asteroid 21 Lutetia, target of Rosetta Mission". Astronomy and Astrophysics 425: L25. doi:10.1051/0004-6361:200400054. 
  11. ^ M. A. Feierberg et al. (1983). "Detection of silicate emission features in the 8- to 13 micrometre spectra of main belt asteroids". Icarus 56: 393. doi:10.1016/0019-1035(83)90160-4. 
  12. ^ A. Dollfus & J. E. Geake (1975). "Polarimetric properties of the lunar surface and its interpretation. VII - Other solar system objects". Proceedings of the 6th Lunar Science Conference, Houston, Texas, March 17–21 3: 2749. 

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