ESA Rosetta Mission: COSIMA collects and analyses Comet 67/P Dust Particles

Two examples of dust grains collected by ESA Rosetta's COmetary Secondary Ion Mass Analyser, (COSIMA) instrument in the period 25-31 October 2014. 

Both grains were collected at a distance of 10-20 km from the comet nucleus. 

Image (a) shows a dust particle (named by the COSIMA team as Eloi) that crumbled into a rubble pile when collected; (b) shows a dust particle that shattered (named Arvid). 

For both grains, the image is shown twice under two different grazing illumination conditions: the top image is illuminated from the right, the bottom image from the left. 

The brightness is adjusted to emphasise the shadows, in order to determine the height of the dust grain. Eloi therefore reaches about 0.1 mm above the target plate; Arvid about 0.06 mm. 

The two small grains at the far right of image (b) are not part of the shattered cluster. The fact that the grains broke apart so easily means their individual parts are not well glued together. 

If they contained ice they would not shatter; instead, the icy component would evaporate off the grain shortly after touching the collecting plate, leaving voids in what remained. 

By comparison, if a pure water-ice grain had struck the detector, then only a dark patch would have been seen. 

These 'fluffy' grains are thought to originate from the dusty layer built up on the comet's surface since its last close approach to the Sun, and will soon be lost into the coma. 

Image courtesy ESA /Rosetta et al

ESA's Rosetta mission is providing unique insight into the life cycle of a comet's dusty surface, watching 67P/Churyumov-Gerasimenko as it sheds the dusty coat it has accumulated over the past four years.

The COmetary Secondary Ion Mass Analyser, (COSIMA), is one of Rosetta's three dust analysis experiments. It started collecting, imaging and measuring the composition of dust particles shortly after the spacecraft arrived at the comet in August 2014.

Results from the first analysis of its data are reported in the journal Nature. "Comet 67P/Churyumov-Gerasimenko sheds dust coat accumulated over the past four years" - Rita Schulz et al. Nature (2015) doi:10.1038/nature14159

The study covers August to October, when the comet moved along its orbit between about 535 million kilometres to 450 million kilometres from the Sun. Rosetta spent the most of this time orbiting the comet at distances of 30 km or less.

The scientists looked at the way that many large dust grains broke apart when they were collected on the instrument's target plate, typically at low speeds of 1-10 m/s.

The grains, which were originally at least 0.05 mm across, fragmented or shattered upon collection.

The fact that they broke apart so easily means that the individual parts were not well bound together. Moreover, if they had contained ice, they would not have shattered.

Instead, the icy component would have evaporated off the grain shortly after touching the collecting plate, leaving voids in what remained.

By comparison, if a pure water-ice grain had struck the detector, then only a dark patch would have been seen.

The dust particles were found to be rich in sodium, sharing the characteristics of 'interplanetary dust particles'.

These are found in meteor streams originating from comets, including the annual Perseids from Comet 109P/Swift-Tuttle and the Leonids from 55P/Tempel-Tuttle.

"We found that the dust particles released first when the comet started to become active again are 'fluffy'.

They don't contain ice, but they do contain a lot of sodium. We have found the parent material of interplanetary dust particles," says lead author Rita Schulz of ESA's Scientific Support Office.

The scientists believe that the grains detected were stranded on the comet's surface after its last perihelion passage, when the flow of gas away from the surface had subsided and was no longer sufficient to lift dust grains from the surface.

While the dust was confined to the surface, the gas continued evaporating at a very low level, coming from ever deeper below the surface during the years that the comet travelled furthest from the Sun.

Effectively, the comet nucleus was 'drying out' on the surface and just below it.

"We believe that these 'fluffy' grains collected by Rosetta originated from the dusty layer built up on the comet's surface since its last close approach to the Sun," explains Martin Hilchenbach, COSIMA principal investigator at the Max-Planck Institute for Solar System research in Germany.

"This layer is being removed as the activity of the comet is increasing again. We see this layer being removed, and we expect it to evolve into a more ice-rich phase in the coming months."

The comet is on a 6.5-year circuit around the Sun, and is moving towards its closest approach in August of this year.

At that point, Rosetta and the comet will be 186 million kilometres from the Sun, between the orbits of Earth and Mars.

As the comet warms, the outflow of gases is increasing and the grains making up the dry surface layers are being lifted into the inner atmosphere, or coma.

Eventually, the incoming solar energy will be high enough to remove all of this old dust, leaving fresher material exposed at the surface.

"In fact, much of the comet's dust mantle should actually be lost by now, and we will soon be looking at grains with very different properties," says Rita.

"Rosetta's dust observations close to the comet nucleus are crucial in helping us to link together what is happening at the very small scale with what we see at much larger scales, as dust is lost into the comet's coma and tail," says Matt Taylor, ESA's Rosetta project scientist.

"For these observations, it really is a case of "watch this space" as we continue to watch in real time how the comet evolves as it approaches the Sun along its orbit over the coming months."

NASA LADEE: Collecting lunar atmosphere data

Artist’s concept of NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft in orbit above the moon as dust scatters light during the lunar sunset. 

Credit: NASA Ames / Dana Berry

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) is ready to begin collecting science data about the moon.

On Nov. 20, the spacecraft successfully entered its planned orbit around the moon's equator—a unique position allowing the small probe to make frequent passes from lunar day to lunar night.

This will provide a full scope of the changes and processes occurring within the moon's tenuous atmosphere.

LADEE now orbits the moon about every two hours at an altitude of eight to 37 miles (12-60 kilometers) above the moon's surface.

For about 100 days, the spacecraft will gather detailed information about the structure and composition of the thin lunar atmosphere and determine whether dust is being lofted into the lunar sky.

Sarah Noble

"A thorough understanding of the characteristics of our lunar neighbour will help researchers understand other small bodies in the solar system, such as asteroids, Mercury, and the moons of outer planets," said Sarah Noble, LADEE program scientist at NASA Headquarters in Washington.

Scientists also will be able to study the conditions in the atmosphere during lunar sunrise and sunset, where previous crewed and robotic missions detected a mysterious glow of rays and streamers reaching high into the lunar sky.

"This is what we've been waiting for – we are already seeing the shape of things to come," said Rick Elphic, LADEE project scientist at NASA's Ames Research Center in Moffett Field, Calif.

Rick Elphic

On Nov. 20, flight controllers in the LADEE Mission Operations Center at Ames confirmed LADEE performed a crucial burn of its orbit control system to lower the spacecraft into its optimal position to enable science collection.

Mission managers will continuously monitor the spacecraft's altitude and make adjustments as necessary.

"Due to the lumpiness of the moon's gravitational field, LADEE's orbit requires significant maintenance activity with maneuvers taking place as often as every three to five days, or as infrequently as once every two weeks," said Butler Hine, LADEE project manager at Ames.

Butler Hine

"LADEE will perform regular orbital maintenance maneuvers to keep the spacecraft's altitude within a safe range above the surface that maximizes the science return."

In addition to science instruments, the spacecraft carried the Lunar Laser Communications Demonstration, NASA's first high-data-rate laser communication system.

It is designed to enable satellite communication at rates similar to those of high-speed fiber optic networks on Earth.

The system was tested successfully during the commissioning phase of the mission, while LADEE was still at a higher altitude.

LADEE was launched Sept. 6 on a U.S. Air Force Minotaur V, an excess ballistic missile converted into a space launch vehicle and operated by Orbital Sciences Corp. of Dulles, Va. LADEE is the first spacecraft designed, developed, built, integrated and tested at Ames.

It also was the first probe launched beyond Earth orbit from NASA's Wallops Flight Facility on the Virginia coast.

More information: For more information about the LADEE mission, visit: www.nasa.gov/ladee

NASA Curiosity Rover Collects First Martian Bedrock Sample

At the center of this image from NASA's Curiosity rover is the hole in a rock called "John Klein" where the rover conducted its first sample drilling on Mars. 

The drilling took place on Feb. 8, 2013, or Sol 182, Curiosity's 182nd Martian day of operations. 

Several preparatory activities with the drill preceded this operation, including a test that produced the shallower hole on the right two days earlier, but the deeper hole resulted from the first use of the drill for rock sample collection. Image credit: NASA/JPL-Caltech/MSSS.

NASA's Curiosity rover has, for the first time, used a drill carried at the end of its robotic arm to bore into a flat, veiny rock on Mars and collect a sample from its interior. This is the first time any robot has drilled into a rock to collect a sample on Mars.

The fresh hole, about 0.63 inch (1.6 centimeters) wide and 2.5 inches (6.4 centimeters) deep in a patch of fine-grained sedimentary bedrock, can be seen in images and other data Curiosity beamed to Earth Saturday. The rock is believed to hold evidence about long-gone wet environments. In pursuit of that evidence, the rover will use its laboratory instruments to analyze rock powder collected by the drill.

"The most advanced planetary robot ever designed is now a fully operating analytical laboratory on Mars," said John Grunsfeld, NASA associate administrator for the agency's Science Mission Directorate. "This is the biggest milestone accomplishment for the Curiosity team since the sky-crane landing last August, another proud day for America."

For the next several days, ground controllers will command the rover's arm to carry out a series of steps to process the sample, ultimately delivering portions to the instruments inside.

"We commanded the first full-depth drilling, and we believe we have collected sufficient material from the rock to meet our objectives of hardware cleaning and sample drop-off," said Avi Okon, drill cognizant engineer at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Rock powder generated during drilling travels up flutes on the bit. The bit assembly has chambers to hold the powder until it can be transferred to the sample-handling mechanisms of the rover's Collection and Handling for In-Situ Martian Rock Analysis (CHIMRA) device.

Before the rock powder is analyzed, some will be used to scour traces of material that may have been deposited onto the hardware while the rover was still on Earth, despite thorough cleaning before launch.

"We'll take the powder we acquired and swish it around to scrub the internal surfaces of the drill bit assembly," said JPL's Scott McCloskey, drill systems engineer. "Then we'll use the arm to transfer the powder out of the drill into the scoop, which will be our first chance to see the acquired sample."

"Building a tool to interact forcefully with unpredictable rocks on Mars required an ambitious development and testing program," said JPL's Louise Jandura, chief engineer for Curiosity's sample system. "To get to the point of making this hole in a rock on Mars, we made eight drills and bored more than 1,200 holes in 20 types of rock on Earth."

Inside the sample-handling device, the powder will be vibrated once or twice over a sieve that screens out any particles larger than six-thousandths of an inch (150 microns) across. Small portions of the sieved sample will fall through ports on the rover deck into the Chemistry and Mineralogy (CheMin) instrument and the Sample Analysis at Mars (SAM) instrument. These instruments then will begin the much-anticipated detailed analysis.

The rock Curiosity drilled is called "John Klein" in memory of a Mars Science Laboratory deputy project manager who died in 2011. Drilling for a sample is the last new activity for NASA's Mars Science Laboratory Project, which is using the car-size Curiosity rover to investigate whether an area within Mars' Gale Crater has ever offered an environment favorable for life.

The MAGIC Cherenkov Telescope Array

The MAGIC Collaboration has built in 2001–2003 a first large atmospheric imaging Cherenkov telescope, MAGIC-I, with a mirror surface of 236 sq.m. and equipped with photo-multiplier tubes of optimal efficiency.

In 2009, a second telescope of essentially the same characteristics was added; MAGIC-II was installed at a distance of 85m from MAGIC-I.

With the accent of these instruments on large mirror surface and best light collection, cosmic gamma-rays at an energy threshold lower than any existing or planned terrestrial gamma-ray telescope have become accessible. So far achieved has been a threshold of 25 GeV.