Cassini Discovers a New Moonlet in Saturn’s Rings

The ~400 meter moonlet casts a 25 mile shadow across Saturn's B-ring (NASA)

The ~400 meter moonlet casts a 25 mile shadow across Saturn's B-ring (NASA)

As Saturn approaches its August 11th equinox (during which the Sun will be directly above the gas giant’s equator at noon for 27 months), the Cassini Equinox Mission can do some moonlet spotting. During this time, sunlight will cast long shadows of any object protruding from the 10 metre-thick rings.

In this case, hidden inside Saturn’s B-ring, a moonlet with a diameter of approximately 400 metres becomes obvious when sunlight hits the rings edge-on. The result is a very obvious 25 mile-long shadow. This discovery wouldn’t have been possible during any other time, as Cassini can only see the small rock because of its shadow. If the Sun was above or below the rings, no shadow would be cast, and therefore no moonlet would be visible.

Saturn experiences an equinox twice every Saturnian year (once every 15 terrestrial years), and NASA planned the Cassini mission to coincide with this interesting period to economise on the position of the Sun, spotting small objects like this little satellite…

Source: Wired, thanks to Helen Middleton (@herroyalmaj).

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Opportunity Investigates Possible Martian Meteorite

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On its epic journey to Endeavour Crater, Mars Expedition Rover (MER) Opportunity passed a suspect looking boulder on July 18th. Dubbed “Block Island” by MER controllers, this dark rock looks very different from its surroundings, so Opportunity has been ordered to go off its planned route by 250 meters and have closer look.

Measuring approximately 0.6 meters across, the jagged specimen could be a meteorite, giving the rover a chance to carry out an in-situ analysis of its composition, determining whether or not this is indeed of extra-martian origin.

The odd-shaped and dark rock sits atop the regolith, and Opportunity will use its APXS instrument to determine its composition (NASA)

The odd-shaped and dark rock sits atop the regolith, and Opportunity will use its APXS instrument to determine its composition (NASA)

The next step is for the rover to extend its robotic arm, pressing the Alpha Particle X-Ray Spectrometer (APXS) up against the rock’s surface. The spectrometer will basically give the sample a blast of radiation, consisting of alpha particles and X-rays. The analysis of scattered alpha particles (after they have bounced off the material) will reveal the mass of the elements they collide with and the emission of X-rays will also reveal a lot about the material.

So could this be a meteorite? We’ll have to wait until the little robot has carried out its experiment… she may be getting old, but Opportunity is still carrying out some awesome science.

Source: NASA

Pluto Could Still Be A Planet! (Who Cares?)

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All right, that title was a little harsh, but I think you get the point. It’s not that I don’t love Pluto, Pluto is a fine little planet… dwarf planet… hold on, plutoid. It holds a certain charm and mystique, plus we have the mother of all NASA missions (New Horizons) gliding its way to the outer icy reaches of the Solar System — the Kuiper Belt to be precise — to take a look at Pluto, up close, for the first time. I can’t wait for 2015 when the spacecraft starts taking snapshots, it will be awesome.

But what of the small planety-thingy’s status? Is it still a planetary outcast, destined for a life on Cosmic Skid Row? Or is Pluto about to get the mother of all reprieves and be re-classified as a planet? Does it really matter?

The reason why I ask is that the whole “demotion” thing was seen as bad news. I actually saw it as an exciting development in Solar System exploration (but hoped it wouldn’t tarnish the little rock’s popularity all the same). In actuality, Pluto is 27% less massive than the recently discovered dwarf planet Eris, so how could Pluto still be called a planet? Should Eris be classified as a planet, then? In light of new dwarf planet discoveries, Pluto became a rounding error and had to be re-classified. The International Astronomical Union drew up some planetary rules and found that Pluto didn’t have the gravitational clout to clear its own orbit and so was re-classified as a dwarf planet in 2006.

Suddenly, Pluto had “fans” that took the re-classification personally and got angry at the IAU for throwing Pluto out of the planetary club. Their reason? Only 4% of IAU members were present for the re-classification vote, they saw it as a personal slight against the “9th planet.” Even the nutty state of Illinois was FURIOUS and reinstated Pluto as a planet… (just in the state of Illinois).

We’ve heard this emotional story of planetary bullying over and over, so I won’t go over the details again. The whole Pluto story has been widely covered, many people pointing the finger at the evil IAU 4%, some have even gone as far as saying this is evidence that there is a growing rift between the public and scientists (let’s take national votes on scientific decisions! That would be fun). But what does it really matter? Really.

Is the Pluto re-classification a breech of our human rights? How about planetary rights? Is it indicative of the number of idiot scientists who voted in the 2006 IAU poll? Is this an indicator of poor scientific thinking? Could a war be sparked over this atrocity? Was it really a ‘bad’ decision?

Just so my opinion is known, I don’t care what Pluto is called. If NASA decided to explode Pluto as part of a Kuiper belt clearing project, then yes, I might be a bit annoyed; I’d even start a blog titled “Save Pluto.” But calling Pluto a dwarf planet (or the rather cute plutino) really doesn’t bother me. It’s a consequence of scientific endeavour, despite the perceived “controversy.” As the legendary astronomer Patrick Moore said, “…you can call it whatever you like!” Pluto is still Pluto.

However, it looks like Pluto might be re-classified again… big yawn.

This time, heavy hitter Alan Stern, Principal Investigator for the New Horizons mission, weighed in with his opinion on the matter. “Any definition that allows a planet in one location but not another is unworkable. Take Earth. Move it to Pluto’s orbit, and it will be instantly disqualified as a planet,” Stern said.

This implies that if Earth was moved to the Kuiper belt, as things move a lot more sluggishly out there, a planet with the gravitational pull of the Earth couldn’t clear its orbit, therefore the “must clear its own orbit” criteria is a bad location-based definition for a planet. (I would argue that there’s every possibility that Earth could clear it’s own orbit at that distance given enough time, but what would I know, I’m no planetary physicist, but everyone seems to have an opinion about Pluto, so there’s mine.)

This analogy is a bit like saying a car driven down a country lane is a car. But a car driven on a freeway is a bike.

There is the counter argument to this case; if there was something as big as Mars, or even Earth, it may have tunnelled out a path through the Kuiper belt, thereby clearing its orbit. Alas, there appears to be no solid consensus as to the nature of this littered volume of space (at least until 2015), hence all the fuss.

Now there’s some big noise that the IAU will reconvene and discuss the Pluto hoopla again, giving a vague glimmer of hope to pro-planet plutonites that the 2006 decision will be overthrown. Alas, I very much doubt that as, quite frankly, there are more pressing (and more interesting) matters to discuss such as: what the hell hit Jupiter?! We should re-classify Jupiter as ‘the inner Solar System’s gaseous protector’!

Source: New Scientist

Spirit And The Amazing Technicolour Dust Devils

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What are they? I’ve seen some odd photos from the Martian surface, but when I first saw this image, the pinks, blues and yellow smudges looked… alien. The surprise probably comes from the fact that we are so used to the rusty red pictures to come from the various rovers, landers and satellites, that any colour not a variation of red comes as a shock.

Although it looks odd, there is in fact a sensible answer to these ghostly splodges on the horizon. This photo was snapped by Mars Expedition Rover (MER) Spirit back on sol 1919 of the MER mission on May 27th, 2009.

Using its panoramic camera (Pancam), Spirit performed a number of exposures, each one using a different colour filter. With some luck during the photography session of the Martian landscape, a dust devil (a mini whirlwind) meandered through the Pancam’s field of view. In each frame taken with different filters, the only feature moving would have been the swirling dust, so that’s why it appears as a different hue than the surrounding landscape.

Dust devils occur on both Mars and on Earth when solar energy heats the surface, resulting in a layer of warm air just above the surface. Since the warmed air is less dense than the cooler atmosphere above it, it rises, making a swirling thermal plume that picks up the fine dust from the surface and carries it up into the atmosphere. This plume of dust moves with the local wind.NASA/JPL

Dust devils have provided some unexpected fun for the rovers, often tuning up unannounced. These make for interesting observations of local weather conditions, but they also provide an essential mini-undusting service for the wheeled robot’s solar panels.

And now they’ve been pictured in technicolour. How nice.

Source: NASA/JPL

I See Mars Faces… Everywhere

The two suspect shapes spotted by Mars conspiracy theorists. Exhibit 1: The Egyptian statue. Exhibit 2: ??

During my search for material for last week’s Wide Angle: Mars Roving on Discovery, I was looking for images snapped by the Mars Exploration Rovers (MER) Spirit and Opportunity. During my trawl around Google Images, I managed to find a high-resolution picture of the rocky outcrop on the side of Victoria Crater when Opportunity was imaging the area in 2006.

I’ve always loved these Victoria images; you can easily see layering in the exposed rock and boulders strewn below. In fact, this could be a black and white picture of the Utah desert, or a wide angle view of the Grand Canyon. But no, this is Mars; lifeless Mars.

Or is it?

One version of the Opportunity image can be found on a conspiracy website, where a ‘study’ has been carried out. And guess what they found?

Oh yes, apparently a Martian civilization worshiped the pharaohs of ancient Egypt, carving a statue more commonly associated with pyramids into the crater wall (“Exhibit A” in the image above). Also, there’s a curiously shaped multi-layer disk on the ground — obviously some kind of alien artifact (“Exhibit B”).

Please.

Normally I’d ignore something like this, but I thought I’d have a little fun one evening (because my evenings simply aren’t exciting enough, it seems). Inspired by Phil Plait’s visions of Miss Piggy in a Mars mesa last week, I wanted to test myself and go on a pareidolia hunt of my own, armed with the Victoria crater pic, my imagination and questionable eyesight.

The human brain is a strange old thing at times, creating recognizable features out of random, inanimate objects, and that is exactly what some people use as “proof” of their nutty theory or visions of the second coming. People see Jesus in burnt toast, Michael Jackson in cloud formations and, in this case, ancient Egyptian statues carved into crater rims on Mars.

So have a look at this, I impressed myself (note the outstanding use of Photoshop):

Mars faces:

What I discovered in this single NASA Mars image:

A: Exhibit A – the Egyptian statue.
B: Exhibit B – some other artifact.
C: Admiral "It’s a trap!" Ackbar from Star Wars: The Empire Strikes Back.
D: Audry II, the blood-drinking plant from Little Shop of Horrors.
E: Jabba the Hutt, or an angry toad.
F: A gorilla’s head (kinda).
G: Can’t remember what I saw in this… but it’s kinda alien looking… right?
H: Insane-looking face. Could be the Mad Hatter?
I: Weird-looking Picasso face.
J: The alien from Predator.
K: Human head.
L: Another Egyptian statue, head part.
M: Humanoid skull!

I’ve even got a full-resolution version in case you can’t see the fruits of my imagination (all 4MB of it). But who cares if you can’t see Jabba, Ackbar, skulls or statues? That’s not the point; most conspiracy sites skew the facts to convince the reader to believe their false claims anyway. Hmmm… I’m quite good at this, perhaps I should start my own ‘Mars Faces’ conspiracy, only including characters from Star Warshmmm.

I’m personally most impressed with the “humanoid skull” (M), “Admiral Ackbar” (C) and the “insane face” (H). Obviously the ancient Martian civilization were a part of the Empire (not so far, far away), carried out sacrifices on humanoids (bones now littering the plains), worshipped Egyptian kings and had killer rock sculpting skills. Obviously.

Want more Mars faces? We have some puzzles on the subject over at Discovery Space! What are the odds…

Venus is Lonely. Very, Very Lonely

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Venus is a hellish world. Although the planet is nearly the same size of Earth, that’s where the similarities end. Having said that, it does have an atmosphere, but it’s not the kind of atmosphere you would ever want to spend time breathing in. Composed of a dense carbon dioxide/nitrogen mix where clouds are made from sulphuric acid, you can forget about Venus as a tropical holiday destination. Even if you found a way to ‘breathe’ on Venus, you’d need to prepare yourself for the scorching 470°C surface temperatures and bone crushing pressures 100 times the pressure we are used to on Earth.

Doesn’t sound like a very nice place does it? Certainly an interesting world, providing us with invaluable science (after all, the reason for the extreme temperatures on Venus is due to a run-away greenhouse effect, it could help us understand the growing problems we are facing with our comparatively mild global warming woes), but an unlikely candidate for human colonization (unless we lived in the clouds).

Venus might not be a popular world for mankind to live on, but it doesn’t seem to be a popular world for natural satellites to orbit around either. It doesn’t have any moons, and astronomers are a little confused as to why this is the case. The only other planet without moons is the innermost terrestrial planet, Mercury. Every other planet in the Solar System has at least one natural satellite.

For hundreds of years, astronomers have been on the lookout for anything orbiting Venus but they’ve had little luck. However, some of the earliest observations of Venus appeared to indicate the presence satellites (in 1645, F. Fontana mentioned the possibility of a satellite discovery, followed by further observations in the late 1600’s and 1700’s). Since 1768, there have been no further reports of any satellite sightings. 1956 was the last published survey for Venusian satellites, using photographic plates, and that survey (published by Gerard Kuiper in 1961) drew up blanks for any satellites measuring over 2.5 km wide.

The lack of Venusian moons is puzzling, as a Venus-moon interacting mechanism has often been invoked as the reason why Venus has a retrograde spin (i.e. viewed from the ‘top’ of the Solar System plane, Venus has a clockwise rotation, whereas the rest of the planets, apart from Uranus — that spins on its side, bizarrely — have an anti-clockwise, or prograde, spin). Perhaps Venus once had a moon, but it has since been lost due to gravitational interactions with other Solar System bodies, or due to tidal instabilities, the innermost terrestrial planets collided with their large satellites a long time ago.

This is where Scott Sheppard from the Carnegie Institution of Washington and Chadwick Trujillo from the Gemini Observatory (Hawaii) step in. In a recent publication titled, “A Survey for Satellites of Venus,” Sheppard and Trujillo pick up where Kuiper left off, and carry out a systematic survey searching for any natural satellites around Venus. Only this time, by using the cutting-edge 6.5 meter telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile, they looked for objects only a few hundred meters in diameter.

The researchers scanned the interior of the Venusian ‘Hill Sphere’ to see if any undiscovered tiny moons were lurking. The Hill sphere is the volume of space surrounding a planetary body where natural satellites can orbit without being destabilized by the gravitational effects of the Sun. If there are any unforeseen moons, they should be found in stable orbits within the Hill sphere.

Sheppard and Trujillo have drawn blanks. Although a few errant asteroids were detected, no natural satellites down to a diameter of 600 meters were discovered. They surveyed 90% of the Venusian Hill sphere, and 99% of the inner Hill sphere (0.7rH) — the volume of space predicted to contain the stable orbits of natural satellites.

This new survey improves the non-detection of satellites down to a factor of 50 on previous studies, thereby proving Venus either, a) never possessed any satellites over 1km in diameter, or b) the orbits of past large satellites have become unstable and crashed into Venus or flung into space.

Either way, Venus remains alone, with only the ESA Venus Express for company

Source: A Survey for Satellites of Venus, Sheppard & Trujillo, 2009. arXiv:0906.2781v1 [astro-ph.EP]

Mars Rover Spirit is Stuck in the Regolith

Spirit is stuck (NASA)

Mars Exploration Rover Spirit is in trouble again. She’s stuck.

The tenacious little robot has suffered traction problems before and has even been dragging around a broken wheel for the last three years, leaving the other five to take up the slack. Then there’s the dust storms that have hindered the life-giving solar panels ability to collect sunlight. And most recently, the on-board computers have been rebooting and Spirit’s flash memory has been forgetting to record data.

A little help here? Spirit has driven into soft ground, burying her wheels halfway. Engineers are working plans to extricate her. –A distress tweet from @MarsRovers

One of Spirit's buried wheels as taken by the front hazard-avoidance camera on Sol 1899, May 6th (NASA)

One of Spirit's buried wheels as taken by the front hazard-avoidance camera on Sol 1899, May 6th (NASA)

Now, she’s stuck in the Martian dirt after slipping backwards down a slope during a series of backward drives around a plateau called “Home Plate.”

Spirit is in a very difficult situation,” JPL project manager John Callas said. “We are proceeding methodically and cautiously. It may be weeks before we try moving Spirit again. Meanwhile, we are using Spirit’s scientific instruments to learn more about the physical properties of the soil that is giving us trouble.”

At JPL, a team have been assembled to try to find a solution to the problem with a model of the situation here on Earth. Unfortunately the wheels are stuck fast, half-buried, and scientists are increasingly worried that any attempts to free the struggling rover could make matters worse. The concern is for the chassis under the robot. Should it make contact with the rocks underneath, it would effectively beach itself, completely losing traction that could be used to free the wheels. In short, the situation is not good, but NASA is working overtime to find ways to get the rover on the road once more.

Fortunately, wind has helped the ailing rover recently, clearing excess dust off the solar panels, giving Spirit a much needed energy boost, but will it be enough to get her out of this difficult situation? If there’s a way, Spirit will find it, as let’s face it, she’s lived through a lot of hard knocks…

Source: NASA, AP

Slow News Day: Alien Skull On Mars

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This just came in from the Telegraph, apparently Mars Exploration Rover Spirit has spotted a random skull on the Martian surface. This is obviously the only interpretation… as we know what an alien looks like, don’t we? Big head, big eyes, pasty grey skin. Something like this? Or, more likely, like this? Or this? Wow, it could be any one of them.

However, it’s not quite that exciting.

It’s a rock, as you may have already guessed. And no, the Telegraph isn’t taking it seriously either. (Although The Sun’s microreport could be taken either way.)

Although the newspaper’s article resembles a badly conditioned April Fools gag, there is one glaring error, well two actually. No, three.

Firstly, Spirit is not a camera – it’s a whole robot with a camera attached (called the Panoramic Camera, or Pancam for short). If it was just a camera, could you imagine the movie location costs?

Second, I’m not sure why this was filed in “Science News”. It obviously needs to be filed under “It’s a Slow News Day, We’ll Report Anything”.

And thirdly, I seriously doubt this image got “space-gazers talking”. When I last looked at one of Opportunity’s panoramic shots, I could see all kinds of strange things in the Mars dirt. If I was a conspiracy theorist, I’d love poking around the shapes and shadows, thinking I could see skulls, flying hubcaps and mysterious plant-like features. But I’m not a conspiracy theorist, I’m a “space-gazer”, but I’m not “talking”.

As it’s late, I’ve given up trying to find the source of the article (no links – come on Telegraph, if you’re gonna play blogging for the day, at least reference your lead!). Apparently some “UFO hunters” were being serious, but then joking, about this rock that looks like a skull. So, what the Telegraph is really trying to tell us is:

A stone. On Mars. Might look like a skull. Doesn’t really. Even ufologists don’t take it seriously. So it’s not really news. Move along.

I’m not suggesting the Telegraph isn’t a good newspaper, on the contrary, but really, what’s the point?

Why did I even bother to report on this? Oh yeah: It’s a stone that looks like a bunny skull. Now try explaining how a rabbit got up there…

Cassini Detects Salt: Enceladus Probably Has a Liquid Ocean

The small icy Saturn moon might have liquid sub-surface oceans after all (NASA)

In October 2008, Cassini flew very close to the surface of Saturn’s icy moon Enceladus. From a distance of only 50 km from the moon, the spacecraft was able to collect samples of a plume of ice. In an earlier “skeet shot”, Cassini captured detailed images of the cracked surface, revealing the source of geysers blasting the water into space. At the time, scientist were able to detect that it was in fact water ice, but little else would be known until the molecular weight of chemicals in the plume could be measured and analysed.

At the European Geophysical Union meeting in Vienna this week, new results from the October Enceladus flyby were presented. Frank Postberg and colleagues from the Max Planck Institute for Nuclear Physics have discovered traces of sodium salts and sodium bicarbonate in the plume for the first time.

It would appear that these chemicals originated in the rocky core of the moon and were leached from the core via liquid water. The water was then transported to the surface where it was ejected, under pressure, into space. Although scientists are aware that the chemical composition in the plume may have originated from an ancient, now frozen, sub-surface ocean, the freezing process would have isolated the salt far from the surface, preventing it from being released.

It is easier to imagine that the salts are present in a liquid ocean below the surface,” said Julie Castillo of NASA’s Jet Propulsion Laboratory in Pasadena, California. “That’s why this detection, if confirmed, is very important.”

This is the best evidence yet that Enceladus does have a liquid ocean, bound to cause a stir amongst planetary scientists and re-ignite excitement for the search for life living in a salty sub-surface ocean.

Source: New Scientist