Asteroid Lutetia May Have A Molten Core


Way out in space, 282 million miles from home, the intrepid ESA Rosetta spacecraft is still busy, but had time to send us an unprecedented view of ancient asteroid Lutetia. On July 10, 2010, Rosetta flew past Lutetia and the results of the imaging revealed surface features which point to an astonishing history. This particular asteroid might not have a “heart of gold”, but it may very well have – or had – a molten interior.

Buzzing by at a speed of 54 000 km/hr and a closest distance of 3170 km, Rosetta took a series of high resolution images and returned them to an international team of researchers from France, Germany, the Netherlands and the United States. By closely examining the craters, cracks and surface, the team was able to determine that Lutetia survived a multitude of impacts – yet retained much of its original structure.

Lutetia fly-by from Science News on Vimeo.

Benjamin Weiss, an associate professor of planetary sciences in MIT’s Department of Earth, Atmospheric and Planetary Sciences, reports Lutetia may have a molten core and this finding shows a “hidden diversity” for known structures within the greater asteroid belt.

“There might be many bodies that have cores and interesting interiors that we never noticed, because they’re covered by unmelted surfaces,” says Weiss, who is a co-author on both Science papers and lead author for the paper in PSS. “The asteroid belt may be more interesting than it seems on the surface.”

Although the encounter was brief, images from the OSIRIS camera revealed some surface features which are believed to be up to 3.6 billion years old – while others appear to be 50-80 million. These ages can be estimated through impact events and the amount and distribution of ejecta. Some of the areas on Lutetia are heavily cratered, implying greater age, while others appear to be landslide events perhaps caused by nearby fractures. While most asteroids are small, light, and have smooth surfaces – Lutetia is different. It appears to be dense, yet relatively porous… a finding that points toward a “dense metallic core, with a once melted interior underneath its fractured crust.”

“We don’t think Lutetia was born looking like this,” says Holger Sierks, of the Max-Planck-Institut für Sonnensystemforschung, Lindau, Germany. “It was probably round when it formed.”

You’ve got to hand it to Rosetta. By being able to study these images, the many teams of scientists now have evidence for a theory developed last year by Weiss, Elkins-Tanton and MIT’s Maria Zuber. By studying chondrite meteorites, they’ve speculated these strongly magnetized samples most likely occurred in an asteroid with a melted, metallic core. If this theory proves to be correct, the Lutetia simply managed to dodge the proverbial bullets and developed with a molten interior.

“The planets … don’t retain a record of these early differentiation processes,” Weiss says. “So this asteroid may be a relic of the first events of melting in a body.”

According to MIT news, Erik Asphaug, a professor of planetary science at the University of California at Santa Cruz, studies “hit-and-run” collisions between early planetary bodies. He says the work by Weiss and his colleagues is a solid step toward resolving how certain asteroids like Lutetia may have evolved.

“We’ve had decades of cartoon speculation, and here’s speculation that’s anchored in physical understanding of how the interiors of these bodies would evolve,” says Asphaug, who was not involved in the research. “It’s like getting through the first 100 pages of a novel, and you don’t know where it’s leading, but it feels like the beginnings of a coherent picture.”

Another Rosetta stone?

Original Story Sources: ESA News Release and MIT News Release.

Rosetta Uncovers a Thick, Dusty Blanket on Lutetia


If you think that asteroids are boring, unchanging rocks floating in space waiting only to crop up in bad science fiction films, think again. Images and data that are being returned from various asteroid flybys – such as those by the Rosetta spacecraft and Hayabusa sample return mission – show that asteroids are dynamic, changing miniature worlds unto themselves.

During the recent flyby of the asteroid 21-Lutetia in July, the ESA’s Rosetta spacecraft took an amazing amount of data. After combing through all of this data over the past few months, astronomers have calculated that the asteroid is covered in a 2000-foot (600 meter)-thick blanket of rocks and dust called regolith. This dust is not unlike the outer layer of the Earth’s Moon, consisting of pulverized material that has accumulated over billions of years.

Rosetta is on a course to meet up with the comet 67P/Churyumov-Gerasimenko in 2014, but the spacecraft is no stranger to asteroid visits – on September 6th, 2008, Rosetta made its closest approach of the asteroid 2867-Steins. During this brief visit, Rosetta came within 500 miles (800km) of the small, diamond-shaped asteroid. Among the discoveries made were a chain of impact craters that were likely caused by the collision with a meteoroid stream, or the impact with another small body.

It then approached 21-Lutetia on July 10th of 2010, monitoring the asteroid with 17 instruments on board the spacecraft.

Rosetta took a number of images of the flyby, as well as examining the asteroid with electromagnetic detectors that covered the gamut from the UV to radio waves. Here’s a short animation showing the flyby:

Dr. Rita Schulz from the ESA Research and Scientific Support Department in the Netherlands presented this new information about 21-Lutetia’s regolith today at the Division for Planetary Sciences meeting in Pasadena, CA. She said that the regolith on the asteroid has been determined to be about 2000 feet (600 meters) thick, and that it resembles the regolith on the Moon. Images from the flyby reveal landslides, boulders, ridges, and other kinds of different geologic (or asterologic?) features.

21-Lutetia was determined by the July flyby to have a large, bowl-shaped impact crater on its surface, as well as an abundance of smaller craters. The thick covering of dust “softens” the sharper edges of impact craters in many of the images taken. Whether or not most asteroids of this size are covered in a similar blanket of material remains to be seen.

Boulders can be seen in this close-up image of 21-Lutetia, as taken by Rosetta during the July flyby. Image Credit: mage credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

In understanding more about asteroids and comets, astronomers are better able to hone their model of how our Solar System formed. By studying the composition and frequency of impacts of various asteroids, they can improve their data of just how things have changed since the primordial Solar System.

You can bet your boulders that Rosetta isn’t the only spacecraft to be making multiple rendezvous missions with the smaller denizens of our Solar System. Close flybys, impacts and landings on asteroids and comets are becoming almost commonplace for spacecraft.

There’s the Deep Impact mission, which slammed a huge copper weight into the comet Tempel 1, and has since been renamed EPOXI and is set to approach the comet Hartley 2. The upcoming approach of Vesta and Ceres by the Dawn mission is very much anticipated, and of course the recent success of the Hayabusa asteroid explorer has been a terrific tale of just how much we stand to learn from the trail of small celestial cairns that lead into our past.

Source: ESA, DPS Press Release

Watch Live Webcast of Rosetta Flyby of Asteroid Lutetia July 10

On July 10, ESA’s Rosetta spacecraft will fly past 21 Lutetia, the largest asteroid ever visited by a satellite. After weeks of maneuvers and optical observations, Rosetta is perfectly lined up to skim by the asteroid only 3,162 km (2,000 miles) away. ESA is hosting a live webcast at 16:00 GMT on July 10. Below is an embedded feed that will go live once the webcast begins.

For more information and a complete timeline of events, check out this ESA web page.

Watch live streaming video from eurospaceagency at

Rosetta is expected to pass Lutetia at a relative speed of 54,000 km/hr. All this takes place 454 million km from Earth. Lutetia is a major scientific target of Rosetta’s mission, so most of the orbiter and lander instruments will be on for flyby, studying the asteroid’s surface, dust environment, exosphere, magnetic field, mass and density.

Rosetta is on its way to a 2014 rendezvous with comet 67P/Churyumov-Gerasimenko.

Crescent Earth as Seen by Comet Chasing Spacecraft

Title this one “Rich Blue Crescent” (as opposed to Pale Blue Dot.) This spectacular image of our home planet was captured by the OSIRIS instrument on ESA’s Rosetta comet chaser today (November 12) at 12:28 GMT from about 633,000 km as the spacecraft approached Earth for the third and final swingby. Closest approach is due at 07:45 GMT, on November 13. You can follow Rosetta’s progress at ESA’s Rosetta site and the Rosetta Blog.

Rosetta to Make Final Earth Flyby Nov. 13th

The comet chasing spacecraft Rosetta will make its third and final swing by the Earth on November 13th to pick up more speed for the last part of a 10-year journey that lies ahead. Its mission is to place a lander on comet 67P/Churyumov-Gerasimenko and chase the comet for an entire year on its orbit around the Sun. The spacecraft will be visible to observers from the ground in certain locations on the Earth. This last flyby will increase the spacecraft’s speed by 3.6 km/s (2.2 miles/s) with respect to the Sun, giving Rosetta the energy it needs to boost it to the outer regions of the Solar System.

Rosetta was launched March 2nd, 2004, and will visit a host of targets on its way to comet 67P/Churyumov-Gerasimenko. Rosetta already paid a visit to asteroid 2867 Steins in September 2008. It will visit comet 21 Lutetia 10 June 2010, after which it will go into hibernation until it reaches its final destination in May 2014.

Once Rosetta arrives at 67P/Churyumov-Gerasimenko, it will deploy its Philae lander on the comet’s nucleus, and continue to orbit and study the comet for an entire year during its closest orbit of the Sun. This is the first mission ever to orbit and land on a comet, and promises to return a wealth of data on cometary interaction with the Sun. Comets also contain mostly undisturbed materials from the formation of the Solar System in their nuclei, so studying their composition gives scientists an look into how our Solar System developed.

During the flyby of Earth in November of 2007, Rosetta took the breathtaking image of the Earth pictured here. This next flyby will give observers on the ground a chance to take a look back at Rosetta. The closest approach will occur on November 13th at 8:45 Central European Time (07:45 UT).

Unfortunately, the spacecraft will only be visible from parts of Europe, South America and Africa, as can be seen in the image below. If you are in these regions during the approach, and have favorable conditions, there is a wealth of observing information on the Rosetta blog, specifically on the posts Tips for Sky Junkies I and Tips for Sky Junkies II. They will also be closely following the flyby on the blog, so you can check there for updates on the eve of the event if you are outside the observable range of the spacecraft.The regions where Rosetta will be visible to observers from the ground. Image Credit: ESA

As always, you can check back with us on Universe Today for more coverage of Rosetta’s journey!

Source: ESA

MESSENGER and other Significant Mission Events in 2008


Today, the MESSENGER spacecraft will perform a significant task in its mission by making its first flyby of Mercury (see more info below). Additionally, other spacecraft that are out doing their jobs in various locations of our solar system will have significant mission events occur in 2008. Let’s take a look at the big events coming up this year.

January 14: MESSENGER Flyby of Mercury

Messenger, the MEercury Surface Space ENvironment GEochemistry and Ranging spacecraft, will be the first spacecraft to visit Mercury in almost 33 years. It will explore and take close-up images of parts of the planet that we’ve never seen before. This is the first of three flybys of Mercury the spacecraft will take before settling into orbit in 2011. MESSENGER’s cameras and other instruments will collect more than 1,200 images and make other observations during this approach, encounter and departure. The closest approach of the flyby will occur at 19:04:42 UTC (2:04:42 EST), but mission managers said pictures from the event may not be released for up to a week.

March 12: Cassini flies through the plume of Enceladus’ geyser

The Cassini spacecraft will fly extremely close to Saturn’s moon Enceladus at an altitude of only 23 km (14 mi), and actually fly through the plume of an active geyser on the moon’s south pole. How such a cold moon could host an area warm enough to have erupting water vapor is a mystery. Scientists are pondering if Enceladus has active ice volcanism, and if so, is it due to ice sublimating, like a comet, or due to a different mechanism, like boiling water as in Old Faithful at Yellowstone. This flyby will help answer those questions.

Cassini will also have several relatively close flybys this year of the moon Titan. The flybys will occur on Feb. 22, March 25, and May 12.

May 25: Phoenix lands on Mars

Phoenix will land in the north polar region of Mars and will help characterize the climate and geology of the Red Planet, as well as possibly determine if live ever arose on Mars. Pursuing NASA’s “Follow the Water” strategy, the lander will dig through soil to reach water ice with its robotic arm and perform numerous scientific experiments. Phoenix launched on Aug. 4, 2007. University of Arizona’s Phoenix page

September 5: Rosetta flyby of Asteroid Steins

The Rosetta spacecraft is on its way to orbit comet 67P Churyumov-Gerasimenko in 2014, but in the meantime it will pass by Asteroid 2867 Steins. During the flyby, Rosetta will study Steins to determine and characterize the asteroid’s surface composition and morphology. Asteroid Steins is roughly 10 km in diameter.