Posted on by Fraser Cain

Storms on Saturn

Storms on Saturn. Image credit: NASA/JPL/SSI

Jupiter is well known for the storms that rage across its upper atmosphere, especially the Great Red Spot. But Saturn has storms too. They’re not as large, intense or large lived, but compared to Earth, they’re enormous. And Saturn has one of the big mysteries in the Solar System; a hexagon-shaped storms at its poles.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

Winds blow hard on Saturn. The highest velocities are near the equator, where easterly blowing winds can reach speeds of 1,800 km/h. The wind speeds drop off as you travel towards the poles.

Like Jupiter, storms can appear in the bands that circle the planet. One of the largest of these was the Great White Spot, observed by the Hubble Space Telescope in 1990. These storms seem to appear once every year on Saturn (once every 30 Earth years).

NASA’s Cassini spacecraft discovered static hexagonal storm circling around Saturn’s north pole, including a clearly defined eyewall – just like a hurricane. Each side on the northern polar hexagon is approximately 13,800 km long, and the whole structure rotates once every 10 hours and 39 minutes; the same as a day on Saturn.

Here’s an article about a time when Cassini tracked a long-lived lightning storm on Saturn, and another about the strange “Dragon Storm” seen in the planet’s southern hemisphere.

Here’s an article about the northern hexagonal storm from MSNBC, and Astronomy Picture of the Day has an image of storm alley on Saturn.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Posted on by Fraser Cain

Mass of Saturn

Cassini's view of Saturn. Image credit: NASA/JPL/SSI

The mass of Saturn is 5.6846×1026 kg. Just for a comparison, this is 95 times the mass of the Earth.

Saturn is much larger than Earth; its equator spans 9.4 times the size of our home planet. And yet, it’s much less dense. In fact, Saturn has such a low density that it would actually float on water if you could find a pool large enough.

And so, even though it’s much larger and more massive than Earth, if you could actually stand on the “surface of Saturn” – which you can’t, there’s no surface – you would only feel 91% of gravity that we feel here on Earth.

Here’s an article from Universe Today explaining just how big planets can get, and an article about how Jupiter and the other gas giants might have gobbled up their moons while they were forming.

Here’s Hubblesite’s News Releases about Saturn, which has more info about the ringed planet, and NASA’s Solar System Exploration guide.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Posted on by Fraser Cain

Is There Life on Saturn?

Color view of Enceladus. Image credit: NASA/JPL/SSI

It’s hard to imagine a planet less hospitable for life than Saturn. The planet is comprised almost entirely hydrogen and helium, with only trace amounts of water ice in its lower cloud deck. Temperatures at the top of the clouds can dip down to -150 C.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

Temperatures do get warmer as you descend into Saturn’s atmosphere, but the pressures increase too. When temperatures are warm enough to have liquid water, the pressure of the atmosphere is the same as several kilometers beneath the ocean on Earth.

To find life, scientists will want to take a good look at Saturn’s moons. They’re comprised of significant amounts of water ice, and their gravitational interaction with Saturn probably keeps their interiors warm. Saturn’s moon Enceladus is known to have geysers of water erupting from its southern pole. It’s possible that it has vast reserves of superheated water beneath an ice crust.

And Saturn’s moon Titan has lakes and seas of hydrocarbons, thought to be the precursors of life. In fact, scientists think that Titan is very similar in composition to the Earth’s early history.

Hydrocarbons have even been detected across the surface of Saturn’s moon Hyperion.

There might not be life on Saturn, but there are enough intriguing locations to explore around the ringed planet to keep astronomers busy for years.

Here’s an article about exotic life that could live on Titan, and another that dismisses the possibility that there’s life on Enceladus.

This is an article from the Guardian about the possibility of life on Enceladus, and hydrocarbons on Hyperion.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Posted on by Fraser Cain

How Old is Saturn?

Color view of Saturn. Image credit: NASA/JPL/SSI

Saturn formed with the rest of the planets 4.6 billion years ago, out of a spinning disk of gas and dust. This dust collapsed down to form the Sun, and planets formed out of the disk around it. This is why all of the planets orbit the Sun in the same direction.

That’s the easy question.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

The more complicated question is, how old are Saturn’s rings? Some parts might be almost as old as the Solar System, but others are being continuously refreshed. The primary theory for the formation of Saturn’s Rings is that a 300 km moon was torn apart by Saturn’s gravity into the ring system that we see today. But that probably happened more than 4 billion years old.

But Saturn’s rings are bright, and almost made of pure water ice. Since infalling dust should have darkened the rings, they might be as young as 100 million years old. Or perhaps they are ancient, but regular collisions between ring objects keep them looking fresh and new.

One interesting note. Astronomers think that the composition of Saturn – 88% hydrogen and 11% helium with other trace elements – almost exactly matches the composition of the early solar nebula. Saturn is like a miniature version of the Solar System.

Here’s an article from Universe Today that discusses how Saturn’s rings could be as old as the Solar System, and another article about how gas giant planets might have consumed many of their moons early on in their history.

Ask an Astronomer has another answer to this question, and another look at the age of the rings from Geology.com.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Posted on by Fraser Cain

Is There Water on Saturn?

Saturn's moon Enceladus behind the rings. Image credit: NASA/JPL/SSI

Saturn is almost entirely hydrogen and helium, but it does have trace amounts of other chemicals, including water. When we look at Saturn, we’re actually seeing the upper cloud tops of Saturn’s atmosphere. These are made of frozen crystals of ammonia.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

But beneath this upper cloud layer, astronomers think there’s a lower cloud deck made of ammonium hydrosulfide and water. There is water, but not very much.

Once you get away from Saturn itself, though, the nearby area has plenty of water. Saturn’s rings are almost entirely made of water ice, in chunks ranging in size from dust to house-sized boulders.

And all of Saturn’s moons have large quantities of water ice. For example, Saturn’s moon Enceladus is thought to have a mantle rich in water ice, surrounding a silicate core. Geysers of water vapor were detected by NASA’s Cassini spacecraft, spraying out of cracks at Enceladus’ southern pole.

If you want to look for water at Saturn, don’t look at the planet itself, but there’s water all around it.

Here’s an article from Universe Today about the plume of water ice coming off of Enceladus, and how Saturn’s environment is driven by ice.

Here’s an article from NASA about the composition of ice at Saturn’s moon Rhea, and the discovery of liquid water on Enceladus.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Posted on by Nancy Atkinson

Theory of Relativity Passes Another Test

Einstein’s theory of General Relativity has been around for 93 years, and it just keeps hanging in there. With advances in technology has come the ability to put the theory under some scrutiny. Recently, taking advantage of a unique cosmic coincidence, as well as a pretty darn good telescope, astronomers looked at the strong gravity from a pair of superdense neutron stars and measured an effect predicted by General Relativity. The theory came through with flying colors.

Einstein’s 1915 theory predicted that in a close system of two very massive objects, such as neutron stars, one object’s gravitational tug, along with an effect of its spinning around its axis, should cause the spin axis of the other to wobble, or precess. Studies of other pulsars in binary systems had indicated that such wobbling occurred, but could not produce precise measurements of the amount of wobbling.

“Measuring the amount of wobbling is what tests the details of Einstein’s theory and gives a benchmark that any alternative gravitational theories must meet,” said Scott Ransom of the National Radio Astronomy Observatory.

The astronomers used the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT) to make a four-year study of a double-star system unlike any other known in the Universe. The system is a pair of neutron stars, both of which are seen as pulsars that emit lighthouse-like beams of radio waves.

“Of about 1700 known pulsars, this is the only case where two pulsars are in orbit around each other,” said Rene Breton, a graduate student at McGill University in Montreal, Canada. In addition, the stars’ orbital plane is aligned nearly perfectly with their line of sight to the Earth, so that one passes behind a doughnut-shaped region of ionized gas surrounding the other, eclipsing the signal from the pulsar in back.

Animation of double pulsar system

The eclipses allowed the astronomers to pin down the geometry of the double-pulsar system and track changes in the orientation of the spin axis of one of them. As one pulsar’s spin axis slowly moved, the pattern of signal blockages as the other passed behind it also changed. The signal from the pulsar in back is absorbed by the ionized gas in the other’s magnetosphere.

The pair of pulsars studied with the GBT is about 1700 light-years from Earth. The average distance between the two is only about twice the distance from the Earth to the Moon. The two orbit each other in just under two and a half hours.

“A system like this, with two very massive objects very close to each other, is precisely the kind of extreme ‘cosmic laboratory’ needed to test Einstein’s prediction,” said Victoria Kaspi, leader of McGill University’s Pulsar Group.

Theories of gravity don’t differ significantly in “ordinary” regions of space such as our own Solar System. In regions of extremely strong gravity fields, such as near a pair of close, massive objects, however, differences are expected to show up. In the binary-pulsar study, General Relativity “passed the test” provided by such an extreme environment, the scientists said.

“It’s not quite right to say that we have now ‘proven’ General Relativity,” Breton said. “However, so far, Einstein’s theory has passed all the tests that have been conducted, including ours.”

Original News Source: Jodrell Bank Observatory

Posted on by Nancy Atkinson

MESSENGER Provides New Insights on Mercury

mercury_plains..Credit: NASA/JHUAP/Arizona State University

Data from the MESSENGER spacecraft’s first flyby of Mercury in January of 2008 are now turning into science results. Several scientists discussed their findings at a press conference today highlighting the MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission, the first spacecraft to visit Mercury since NASA’s Mariner 10 made three flyby passes in 1974 and 1975. Among the findings, scientists discovered volcanism has played a more extensive role in shaping the surface of Mercury than previously thought. MESSENGER data has also identified and mapped surface rock units that
correspond to lava flows, volcanos, and other geological features, showing an apparent planet-wide iron deficiency in Mercury’s surface rocks. Additionally, other instruments made the first observations about the surface and atmospheric composition of the closest world to the sun.

“We have now imaged half of the part of Mercury that was never seen by Mariner 10,” says Mark S. Robinson of Arizona State University, lead author of s study on composition variations in Mercury’s surface rocks using their multispectral colors. “The picture is still incomplete, but we’ll get the other half on October 6th.”

MESSENGER will make two more Mercury flybys (October 6, 2008 and September 29, 2009) before
going into orbit around the planet, March 18, 2011.

MESSENGER’s big-picture finding, says Robinson, is the widespread role played by volcanism. While impact craters are common, and at first glance Mercury still resembles the Moon, much of the planet has been resurfaced through volcanic activity.

“For example, according to our color data the Caloris impact basin is completely filled with smooth plains material that appears volcanic in origin,” Robinson explains. “In shape and form these deposits are very similar to the mare basalt flows on the Moon. But unlike the Moon, Mercury’s smooth plains are low in iron, and thus represent a relatively unusual rock type.”

Mercury’s surface also has a mysterious, widespread low-reflective material Robinson says, “It’s an important and widespread rock that occurs deep in the crust as well as at the surface, yet it has very little ferrous iron in its silicate minerals.”

Another experiment measured the charged particles in the planet Mercury’s magnetic field, which enabled the first observations about the surface and atmospheric composition of Mercury. “We now know more about what Mercury’s made of than ever before,” said Thomas Zurbuchen, a professor at the University of Michigan. “Holy cow, we found way more than we expected!”

Zurbuchen is project leader of the Fast Imaging Plasma Spectrometer (FIPS), a soda can-sized sensor on board the MESSENGER spacecraft.

FIPS detected silicon, sodium, sulfur and even water ions around Mercury. Ions are atoms or molecules that have lost electrons and therefore have an electric charge.

Because of the quantities of these molecules that scientists detected in Mercury’s space environment, they surmise that they were blasted from the surface or exosphere by the solar wind. The solar wind is a stream of charged particles emanating from the sun. It buffets Mercury, which is 2/3 closer to the sun than the Earth, and it causes particles from Mercury’s surface and atmosphere to sputter into space. FIPS measured these sputtered particles.

Mercury and MESSENGER form the subject of 11 papers in a special section devoted to the January flyby in the July 4, 2008, issue of the scientific journal Science.

News Sources: University of Arizona, MESSENGER site

Posted on by Fraser Cain

Carnival of Space #61

Tunguska Death Ray

[/caption]
This week the Carnival of Space moves to Mang’s Bat Page for the Tunguska edition.

Click here to read the Carnival of Space #61

And if you’re interested in looking back, here’s an archive to all the past carnivals of space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let me know if you can be a host, and I’ll schedule you into the calendar.

Finally, if you run a space-related blog, please post a link to the Carnival of Space. Help us get the word out.

Posted on by Nancy Atkinson

International Group Studies Mars Sample Return Mission

Until humans can actually set foot on the Red Planet, the next best thing would be a sample return mission, to bring Martian soil samples back to Earth. A sample return would exponentially increase our knowledge and understanding Mars and its environment. And in order to pull off a mission of this magnitude, international cooperation might be required, and in fact, may be preferred. The International Mars Exploration Working Group (IMEWG), organized an international committee to study an international architecture for a Mars Sample Return (MSR) mission concept. After several months of collective work by scientists and engineers from several countries worldwide, the “iMARS” group is ready to publish the outcome of its deliberations and the envisioned common architecture for a future international MSR mission, and they will discuss their findings at an international conference on July 9 and 10 in France.

The conference will be held at the Auditorium of the Bibliothèque Nationale de France in Paris, and will bring together members of the scientific and industrial communities as well as representatives of space agencies around the world to discuss the status and prospects for Mars exploration over the coming decades. Attendees will have the opportunity to hear the current international thinking on Mars Sample Return and to interact with key players in the global endeavor of exploring and understanding Mars.

A Mars Sample Return mission would use robotic systems and a Mars ascent rocket to collect and send samples of Martian rocks, soils, and atmosphere to Earth for detailed chemical and physical analysis. Researchers on Earth could measure chemical and physical characteristics much more precisely than they could by via remote control. On Earth, they would have the flexibility to make changes as needed for intricate sample preparation, instrumentation, and analysis if they encountered unexpected results. In addition, for decades to come, the collected Mars rocks could yield new discoveries as future generations of researchers apply new technologies in studying them.

Keynote speakers at the upcoming conferencewill are Steve Squyres of Cornell University, principal investigator under the MER mission, and Jean-Pierre Bibring of the Institut d’Astrophysique Spatiale, principal investigator for a key instrument on Mars Express.

Interested in attending? Check out their website

Original News Source: ESA

Posted on by Nancy Atkinson

Explosive Spacewalk?

Explosive bolts that help detach the Russian Soyuz capsule from the International Space Station may be the source of the problems the spacecraft has encountered during the last two landings. Investigative space journalist and Jim Oberg at MSNBC, who is one of the best experts on the inner workings of the Russian space program recently wrote a very interesting article detailing Russian engineers’ plans to fix the problem: have two Russian cosmonauts conduct a spacewalk on July 10 to remove one of the explosive bolts and bring it inside the space station. The bolts, Oberg says, packs twice the explosive force of an M-80 firecracker when ignited, and the cosmonauts will be handling the bolts directly during what will be a very delicate, if not dramatic, operation.

Oberg reports that Russian space engineers say the bolts at one particular location failed to work properly during each of the two previous Soyuz landings, in October 2007 and then in April 2008. As a result, in each case the landing capsule was twisted out of proper orientation and underwent excess heating on unshielded surfaces before tearing loose from the propulsion module and falling to Earth.

NASA has scheduled a press briefing on July 8 to discuss the spacewalk, but Oberg uncovered details about the spacewalk from status reports and discussions with NASA engineers. The engineers in Houston said that, to their knowledge, no such pyrotechnic device has ever been brought into the space station in its 10-year history.

There are five pairs of explosive bolts that break the connections between the spacecraft’s crew capsule and its propulsion module during descent. Russian experts told NASA at one particular location, position 5, apparently failed to fire during both previous Soyuz descents, preventing a clean separation.

The two cosmonauts, station commander Sergey Volkov and flight engineer Oleg Konenenko will remove the position 5 bolt and place it in a shielded safety canister that was brought to the ISS on the last shuttle mission in May for this spacewalk. So obviously, the plan for this spacewalk has been in the works for quite some time.

Russians engineers assured NASA that the remaining four latches will be adequate to hold the two modules together during any other maneuvers in space.

Check out Jim’s article for more details.