European Association for Astronomy Education

Source: NASA

Mars Odyssey and Mars. Image credit: NASA/JPL.

NASA's Mars Odyssey, which launched in 2001, will break the record Wednesday for longest-serving spacecraft at the Red Planet. The probe begins its 3,340th day in Martian orbit at 5:55 p.m. PST (8:55 p.m. EST) on Wednesday to break the record set by NASA's Mars Global Surveyor, which orbited Mars from 1997 to 2006.

Odyssey's longevity enables continued science, including the monitoring of seasonal changes on Mars from year to year and the most detailed maps ever made of most of the planet. In 2002, the spacecraft detected hydrogen just below the surface throughout Mars' high-latitude regions. The deduction that the hydrogen is in frozen water prompted NASA's Phoenix Mars Lander mission, which confirmed the theory in 2008. Odyssey also carried the first experiment sent to Mars specifically to prepare for human missions, and found radiation levels around the planet from solar flares and cosmic rays are two to three times higher than around Earth.

Odyssey also has served as a communication relay, handling most of the data sent home by Phoenix and NASA's Mars Exploration Rovers Spirit and Opportunity. Odyssey became the middle link for continuous observation of Martian weather by NASA's Mars Global Surveyor and NASA's Mars Reconnaissance Orbiter.

"Odyssey has proved itself to be a great spacecraft, but what really enables a spacecraft to reach this sort of accomplishment is the people behind it," said Gaylon McSmith, Odyssey project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This is a tribute to the whole Odyssey team."

Odyssey will support the 2012 landing of the Mars Science Laboratory and surface operations of that mission. Mars Science Laboratory, also known as the Curiosity rover, will assess whether its landing area has had environmental conditions favorable for microbial life and preserving evidence about whether life has existed there. The rover will carry the largest, most advanced set of instruments for scientific studies ever sent to the Martian surface.

"The Mars program clearly demonstrates that world-class science coupled with sound and creative engineering equals success and longevity," said Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters in Washington.

Other recent NASA spacecraft at Mars include the Mars Global Surveyor that began orbiting the Red Planet in 1997. The Spirit and Opportunity rovers landed on Mars in January 2004. They have been exploring for six years, far surpassing their original 90-day mission. Phoenix landed May 25, 2008, farther north than any previous spacecraft to the planet's surface. The mission's biggest surprise was the discovery of perchlorate, an oxidizing chemical on Earth that is food for some microbes, but potentially toxic for others. The solar-powered lander completed its three-month mission and kept working until sunlight waned two months later. MRO arrived at Mars in 2006 on a search for evidence that water persisted on the planet's surface for a long period of time.

Source: ESA Space Science News

New software developed by ESA makes available online to everyone, everywhere at anytime, the entire library of images from the SOHO solar and heliospheric observatory. Just download the viewer and begin exploring the Sun.

A screenshot from the program JHelioviewer, developed by ESA.
Image credits: ESA JHelioviewer Team

Helioviewer is new visualisation software that enables everyone to explore the Sun. Developed as part of the ESA/NASA Helioviewer Project, it provides a desktop program that enables users to call up images of the Sun from the past 15 years. More than a million images from SOHO can already be accessed, and new images from NASA’s Solar Dynamics Observatory are being added every day. The downloadable JHelioviewer is complemented by the website Helioviewer.org, a web-based image browser.

Helioviewer is new visualisation software that enables everyone to explore the Sun. Developed as part of the ESA/NASA Helioviewer Project, it provides a desktop program that enables users to call up images of the Sun from the past 15 years. More than a million images from SOHO can already be accessed, and new images from NASA’s Solar Dynamics Observatory are being added every day. The downloadable JHelioviewer is complemented by the website Helioviewer.org, a web-based image browser.

Another  screenshot from the program JHelioviewer, developed by ESA.
Image credits: ESA JHelioviewer Team

JHelioviewer is written in the Java programming language, hence the ‘J’ at the beginning of its name. It is open-source software, meaning that all its components are freely available so others can help to improve the program. The code can even be reused for other purposes; it is already being used for Mars data and in medical research. This is because JHelioviewer does not need to download entire datasets, which can often be huge – it can just choose enough data to stream smoothly over the Internet.  (read more)

Source: ESA/Hubble

Hubble's image of SNR B0509-67.5.
Image credit:NASA, ESA, and the Hubble Heritage Team (STScI/AURA).
Acknowledgement: J. Hughes (Rutgers University)

Hubble has spotted a festive bauble of gas in our neighbouring galaxy, the Large Magellanic Cloud. Formed in the aftermath of a supernova explosion that took place four centuries ago, this sphere of gas has been snapped in a series of observations made between 2006 and 2010.

The delicate shell, photographed by the NASA/ESA Hubble Space Telescope, appears to float serenely in the depths of space, but this apparent calm hides an inner turmoil. The gaseous envelope formed as the expanding blast wave and ejected material from a supernova tore through the nearby interstellar medium. Called SNR B0509-67.5 (or SNR 0509 for short), the bubble is the visible remnant of a powerful stellar explosion in the Large Magellanic Cloud (LMC), a small galaxy about 160 000 light-years from Earth.

Ripples seen in the shell’s surface may be caused either by subtle variations in the density of the ambient interstellar gas, or possibly be driven from the interior by fragments from the initial explosion. The bubble-shaped shroud of gas is 23 light-years across and is expanding at more than 18 million km/h.

Astronomers have concluded that the explosion was an example of an especially energetic and bright variety of supernova. Known as Type Ia, such supernova events are thought to result when a white dwarf star in a binary system robs its partner of material, taking on more mass than it is able to handle, so that it eventually explodes.(read more)

Source: ESO Science Release eso1049

Artist’s impression shows a dark gamma-ray burst in a star forming region.
Image credit: ESO/L.Calçada

Gamma-ray bursts are among the most energetic events in the Universe, but some appear curiously faint in visible light. The biggest study to date of these so-called dark gamma-ray bursts, using the GROND instrument on the 2.2-metre MPG/ESO telescope at La Silla in Chile, has found that these gigantic explosions don’t require exotic explanations. Their faintness is now fully explained by a combination of causes, the most important of which is the presence of dust between the Earth and the explosion. (read more)

Source: NASA

Locations of key events are labeled in this extreme ultraviolet image of the sun,
obtained by the Solar Dynamics Observatory on August 1st.
White lines trace the sun's magnetic field.
Image credit: K Schrijver & A. Title

On August 1, 2010, an entire hemisphere of the sun erupted. Filaments of magnetism snapped and exploded, shock waves raced across the stellar surface, billion-ton clouds of hot gas billowed into space. Astronomers knew they had witnessed something big.

It was so big, it may have shattered old ideas about solar activity.

"The August 1st event really opened our eyes," says Karel Schrijver of Lockheed Martin’s Solar and Astrophysics Lab in Palo Alto, CA. "We see that solar storms can be global events, playing out on scales we scarcely imagined before."

For the past three months, Schrijver has been working with fellow Lockheed-Martin solar physicist Alan Title to understand what happened during the "Great Eruption." They had plenty of data: The event was recorded in unprecedented detail by NASA's Solar Dynamics Observatory and twin STEREO spacecraft. With several colleagues present to offer commentary, they outlined their findings at a press conference today at the American Geophysical Union meeting in San Francisco.

Explosions on the sun are not localized or isolated events, they announced. Instead, solar activity is interconnected by magnetism over breathtaking distances. Solar flares, tsunamis, coronal mass ejections--they can go off all at once, hundreds of thousands of miles apart, in a dizzyingly-complex concert of violence.

"To predict eruptions we can no longer focus on the magnetic fields of isolated active regions," says Title, "we have to know the surface magnetic field of practically the entire sun."

This revelation increases the work load for space weather forecasters, but it also increases the potential accuracy of their forecasts.(read more)

Source: NASA/Cassini Mission

NASA's Cassini spacecraft has found possible ice volcanoes on Saturn's moon Titan that are similar in shape to those on Earth that spew molten rock.

Image of a Cassini flyover of an area of Saturn's moon Titan known as Sotra Facula.
Image credit: NASA/JPL-Caltech/USGS/University of Arizona

Topography and surface composition data have enabled scientists to make the best case yet in the outer solar system for an Earth-like volcano landform that erupts in ice. The results were presented today at the American Geophysical Union meeting in San Francisco.

"When we look at our new 3-D map of Sotra Facula on Titan, we are struck by its resemblance to volcanoes like Mt. Etna in Italy, Laki in Iceland and even some small volcanic cones and flows near my hometown of Flagstaff," said Randolph Kirk, who led the 3-D mapping work, and is a Cassini radar team member and geophysicist at the U.S. Geological Survey (USGS) Astrogeology Science Center in Flagstaff, Ariz.

Scientists have been debating for years whether ice volcanoes, also called cryovolcanoes, exist on ice-rich moons, and if they do, what their characteristics are. The working definition assumes some kind of subterranean geological activity warms the cold environment enough to melt part of the satellite's interior and sends slushy ice or other materials through an opening in the surface. Volcanoes on Jupiter's moon Io and Earth spew silicate lava.

Some cryovolcanoes bear little resemblance to terrestrial volcanoes, such as the tiger stripes at Saturn's moon Enceladus, where long fissures spray jets of water and icy particles that leave little trace on the surface. At other sites, eruption of denser materials might build up volcanic peaks or finger-like flows. But when such flows were spotted on Titan in the past, theories explained them as non-volcanic processes, such as rivers depositing sediment. At Sotra, however, cryovolcanism is the best explanation for two peaks more than 1,000 meters (3,000 feet) high with deep volcanic craters and finger-like flows.

"This is the very best evidence, by far, for volcanic topography anywhere documented on an icy satellite," said Jeffrey Kargel, a planetary scientist at the University of Arizona, Tucson. "It's possible the mountains are tectonic in origin, but the interpretation of cryovolcano is a much simpler, more consistent explanation."

Kirk and colleagues analyzed new Cassini radar images. His USGS group created the topographic map and 3-D flyover images of Sotra Facula. Data from Cassini's visual and infrared mapping spectrometer revealed the lobed flows had a composition different from the surrounding surface. Scientists have no evidence of current activity at Sotra, but they plan to monitor the area.

"Cryovolcanoes help explain the geological forces sculpting some of these exotic places in our solar system," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "At Titan, for instance, they explain how methane can be continually replenished in the atmosphere when the sun is constantly breaking that molecule down."

Cassini launched Oct. 15, 1997, and began orbiting Saturn in 2004. Saturn has more than 60 known moons, with Titan being the largest. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency (ASI). JPL manages the mission for NASA's Science Mission Directorate at the agency's Headquarters in Washington.

Source: NASA/JPL Press Release

A new analysis based on data from NASA's Cassini spacecraft finds a causal link between mysterious, periodic signals from Saturn's magnetic field and explosions of hot ionized gas, known as plasma, around the planet.

Artist's concept of the Saturnian plasma sheet.
Credit: NASA/JPL/JHUAPL

Scientists have found that enormous clouds of plasma periodically bloom around Saturn and move around the planet like an unbalanced load of laundry on spin cycle. The movement of this hot plasma produces a repeating signature "thump" in measurements of Saturn's rotating magnetic environment and helps to illustrate why scientists have had such a difficult time measuring the length of a day on Saturn.

"This is a breakthrough that may point us to the origin of the mysteriously changing periodicities that cloud the true rotation period of Saturn," said Pontus Brandt, the lead author on the paper and a Cassini team scientist based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "The big question now is why these explosions occur periodically."

The data show how plasma injections, electrical currents and Saturn's magnetic field -- phenomena that are invisible to the human eye -- are partners in an intricate choreography. Periodic plasma explosions form islands of pressure that rotate around Saturn. The islands of pressure "inflate" the magnetic field.

A new animation showing the linked behavior is available at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

The visualization shows how invisible hot plasma in Saturn's magnetosphere – the magnetic bubble around the planet -- explodes and distorts magnetic field lines in response to the pressure. Saturn's magnetosphere is not a perfect bubble because it is blown back by the force of the solar wind, which contains charged particles streaming off the sun.

The force of the solar wind stretches the magnetic field of the side of Saturn facing away from the sun into a so-called magnetotail. The collapse of the magnetotail appears to kick off a process that causes the hot plasma bursts, which in turn inflate the magnetic field in the inner magnetosphere.

Scientists are still investigating what causes Saturn's magnetotail to collapse, but there are strong indications that cold, dense plasma originally from Saturn's moon Enceladus rotates with Saturn. Centrifugal forces stretch the magnetic field until part of the tail snaps back.

The snapping back heats plasma around Saturn and the heated plasma becomes trapped in the magnetic field. It rotates around the planet in islands at the speed of about 100 kilometers per second (200,000 mph). In the same way that high and low pressure systems on Earth cause winds, the high pressures of space cause electrical currents. Currents cause magnetic field distortions.

A radio signal known as Saturn Kilometric Radiation, which scientists have used to estimate the length of a day on Saturn, is intimately linked to the behavior of Saturn's magnetic field. Because Saturn has no surface or fixed point to clock its rotation rate, scientists inferred the rotation rate from timing the peaks in this type of radio emission, which is assumed to surge with each rotation of a planet. This method has worked for Jupiter, but the Saturn signals have varied. Measurements from the early 1980s taken by NASA's Voyager spacecraft, data obtained in 2000 by the ESA/NASA Ulysses mission, and Cassini data from about 2003 to the present differ by a small, but significant degree. As a result, scientists are not sure how long a Saturn day is.

"What's important about this new work is that scientists are beginning to describe the global, causal relationships between some of the complex, invisible forces that shape the Saturn environment," said Marcia Burton, the Cassini fields and particles investigation scientist at NASA's Jet Propulsion Laboratory, Pasadena, California "The new results still don't give us the length of a Saturn day, but they do give us important clues to begin figuring it out. The Saturn day length, or Saturn's rotation rate, is important for determining fundamental properties of Saturn, like the structure of its interior and the speed of its winds."

Plasma is invisible to the human eye. But the ion and neutral camera on Cassini's magnetospheric imaging instrument provides a three-dimensional view by detecting energetic neutral atoms emitted from the plasma clouds around Saturn. Energetic neutral atoms form when cold, neutral gas collides with electrically-charged particles in a cloud of plasma. The resulting particles are neutrally charged, so they are able to escape magnetic fields and zoom off into space. The emission of these particles often occurs in the magnetic fields surrounding planets.

By stringing together images obtained every half hour, scientists produced movies of plasma as it drifted around the planet. Scientists used these images to reconstruct the 3-D pressure produced by the plasma clouds, and supplemented those results with plasma pressures derived from the Cassini plasma spectrometer. Once scientists understood the pressure and its evolution, they could calculate the associated magnetic field perturbations along the Cassini flight path. The calculated field perturbation matched the observed magnetic field "thumps" perfectly, confirming the source of the field oscillations.

"We all know that changing rotation periods have been observed at pulsars, millions of light years from our solar system, and now we find that a similar phenomenon is observed right here at Saturn," said Tom Krimigis, principal investigator of the magnetospheric imaging instrument, also based at the Applied Physics Laboratory and the Academy of Athens, Greece. "With instruments right at the spot where it's happening, we can tell that plasma flows and complex current systems can mask the real rotation period of the central body. That's how observations in our solar system help us understand what is seen in distant astrophysical objects."