Venus Express observation of Venus, solar wind blowing atmospheric gases into space (ESA)
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We’ve heard about the possibility of extraterrestrial life arriving on Earth from another planet, asteroid or comet, but the mode of transport usually includes a chunk of rock falling through the atmosphere as a meteorite. But there could be another form of interplanetary transportation. What if there are microbial forms of alien life floating in the upper atmosphere of Venus (the planet’s clouds contain compounds that could indicate presence of micro organisms)? Could they make the trip to Earth? Apparently it is possible, if Earth and Venus are correctly aligned, the solar wind may carry microbes from the upstream Venus to downstream Earth in a matter of days…
Earth and Venus are often referred to as ‘sisters’ as their size and geology are very similar. Although the Venusian surface may appear unsuitable for life to thrive (the temperature and atmospheric pressures are very extreme), it may be possible that microbial life exists in the clouds. As Nancy pointed out in her recent article about colonizing Venus, the environment 50 km above the Venusian surface is the most terrestrial-like in the whole of the Solar System (except Earth of course).
So it should come as no surprise that some scientists believe this may be a good location to search for the most basic forms of life. Two such scientists are Prof Chandra Wickramasinghe and Dr Janaki Wickramasinghe from the Cardiff Centre for Astrobiology, UK, who believe the chemical composition of Venus clouds are consistent with the presence of micro-organisms. Their research uses data from Venus Express (launched by ESA in 2005) which is currently orbiting the planet, trying to understand why Venus is so different from the Earth after 4.6 billion years of planetary evolution.
So the Wickramasinghe’s think that Venus and Earth are not only geologically similar, they may be biologically similar too. “Venus and Earth have often been referred to as sisters because of their geological similarities. Our research proposes that the two sisters may be biologically interconnected as well,” Chandra says. But they don’t stop there. If life does exist in the Venusian cloud tops, perhaps these micro organisms can survive the trip through space, seeding the terrestrial atmosphere. Naturally, this can only occur if the planets are in alignment, so the solar wind can erode the Venus atmosphere, transporting microbes as it does so.
However, the life on Venus theory has its critics. “The idea of life on Venus, particularly the clouds where the temperature and pressure are similar to the Earth, has been floated around for a while but is not really very likely,” says Prof Fred Taylor, a planetary scientist at Oxford University.
This is however an interesting field of research that may go to some way in explaining the phrase and book title: “Men Are From Mars, Women Are From Venus.” So, looking for life on Mars and Venus doesn’t seem so outrageous after all…
(A thank you goes to my friend Ross Fenion who sent me the lead to this story and made the “…Women Are From Venus” link, it wasn’t me…)
Spiral galaxy NGC 2770 with two supernovae SN 2007uy and SN 2008D. Credit: NASA
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Just when we thought we were beginning to understand what supernovae and gamma ray bursts were all about. Astronomers have just uncovered the true nature of what they thought was a regular supernova observed in January. At the time, it looked like a supernova emitting a 5-minute long burst of X-rays. But these X-rays were of a lower energy (known as “soft” X-rays) than expected leading some to believe this was a normal emission from a supernova explosion that was being observed during detonation (astronomers don’t usually get the chance to observe a star as it explodes and usually have to make do with analysing the supernova remnant). However, it is now believed this strange supernova event may have been emissions from a dying star at an intermediate mass, neither producing a supernova nor a gamma ray burst, but a combination of both…
Orbiting above Earth on January 9th 2008, the NASA/STFC/ASI Swift telescope caught a rare glimpse of what seemed to be a “normal” supernova at the precise moment of detonation. This observation was completely by luck, as Swift was already observing a supernova remnant (SN 2007uy) in spiral galaxy NGC 2770 that had exploded the previous year (90 million light-years away near the Lynx constellation). Then, as Swift was retrieving data from the SN 2007uy remnant, SN 2008D blasted a 5-minute long burst of X-rays in the same galaxy making this the first supernova to be directly observed.
However, looks can be deceiving. Researchers from a host of institutions including Italian National Institute for Astrophysics (INAF), the Max-Planck Institute for Astrophysics (MPA) and the European Southern Observatory (ESO) have analysed the supernova data thoroughly and at first agreed with the original assessment that it was indeed “normal.”
“What made this event very interesting is that the X-ray signal was very weak and ‘soft’, very different from a gamma-ray burst and more in line with what is expected from a normal supernova.” – Paolo Mazzali, INAF’s Padova Observatory/MPA, research leader.
Artist impression of the twin jets from a GRB. Credit: Dana Berry/SkyWorks Digital
However, astronomers at the Asiago Observatory in Northern Italy had designated the event as a Type 1c supernova, more commonly associated with long-period gamma-ray bursts. Type 1c supernovae are generated by hydrogen-poor progenitor stars with helium-rich outer layers prior to exploding at the end of their lives. But SN 2008D generated soft X-rays more associated with smaller stellar explosions. Therefore SN 2008D was probably produced by a star that was massive at birth (approximately 30 solar masses), rapidly using up its hydrogen fuel in its short life until it was only 8-10 solar masses. At this point it exploded, probably creating a remnant black hole. This chain of thought has led Paolo Mazzali and his team to think SN 2008D was produced by an object of a mass at the boundary of a normal supernova and gamma-ray burst.
“Since the masses and energies involved are smaller than in every known gamma-ray burst related supernova, we think that the collapse of the star gave rise to a weak jet, and that the presence of the Helium layer made it even more difficult for the jet to remain collimated, so that when it emerged from the stellar surface the [X-ray] signal was weak.” – Massimo Della Valle, co-investigator.
Researcher and co-author Stefano Valenti points out that this discovery indicates that all black hole-producing supernovae have the potential to be gamma-ray burst progenitors. “The scenario we propose implies that gamma-ray burst-like inner engine activity exists in all supernovae that form a black hole,” he added.
This week, the Carnival of Space returns to the Music of the Spheres. This is the edition that helps you understand, just how mind-bogglingly large space really is.
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.
[/caption]Greetings, fellow SkyWatchers! Now that the Moon is gone from the early evening skies and I’m back from that soul vacation, tracing my way across the constellations it’s time to break out binoculars and telescopes and enjoy some of the summer’s finest globular clusters – both easy and challenging. For everyone, it’s also time to get back in our atmosphere with drops of Jupiter in our hair and check out the Mighty Jove as it smokes up the sky. Are you ready to dance?
Friday, July 25 – Today in 1971, Apollo 15 was launched on its way to the Moon, and tonight we’ll launch our way north to the Mighty Hercules for a look at another globular study – M92. Although in a relatively open field for starhoppers, it’s not too hard to find if you can imagine it as the apex of a triangle with the northern keystone stars – Eta and Pi – as the base (RA 17 17 07 Dec +43 08 11).
At near magnitude 6, Class IV M92 was discovered by Johann Bode in 1777 and cataloged as Bode 76. Independently recovered by Messier in 1781 and resolved by Herschel in 1783, this bright, compact globular is around 26,700 light-years away and is about 12 to 14 billion years old. It contains 14 RR Lyrae variables among its 330,000 stars and also a very rare eclipsing binary. Viewable unaided under the right conditions and very impressive in even small binoculars, M92 is a true delight to even the smallest of telescopes. It has a very bright and unresolvable core with many outlying stars that are easily revealed. Larger scopes will appreciate its fiery appearance!
Now let’s hop south to Beta Ophiuchi to have a look at NGC 6426 about a fingerwidth south (RA 17 44 54 Dec +-3 10 12). There’s a very good reason why you’ll want to at least try with Herschel II.587. Discovered by Sir William in 1786, this 11th magnitude Class IX globular looks destroyed in comparison to M92. At 67,500 light-years away, it is more than twice the distance from us as M92! Residing 47,600 light-years from the galactic center, NGC 6426 contains 15 RR Lyrae variables (three of which are newly-discovered), and is the most metal-poor globular known. So what’s the relation to M92? It’s even a little bit older!
Forget about finding this one in binoculars and very small telescopes. For the mid-sized scope you’ll find it conveniently located about halfway between Beta and Gamma Ophiuchi – but it’s not easy. Faint and diffuse, a large telescope is required to begin resolution.
Saturday, July 26– For hardcore observers, tonight’s globular cluster study will require at least a mid-aperture telescope, because we’re staying up a bit later to go for a pair that can be seen in the same low power field – NGC 6522 and NGC 6528. You will find them easily at low power just a breath northwest of Gamma Sagittarii (Al Nasl), or the tip of the “teapot’s” spout. Once located, switch to higher power to keep the light of Gamma out of the field and let’s do some studying.
The brighter, and slightly larger, of the pair to the northeast is Class VI NGC 6522 (RA 18 03 34 Dec 30 02 02). Note its level of concentration compared to Class V NGC 6528 (RA 18 04 49 Dec 30 03 20). Both are located around 2,000 light-years from the galactic center, and are seen through a very special area of the sky known as “Baade’s Window” – one of the few areas toward our galaxy’s core region not obscured by dark dust. While they are similar in concentration, distance, etc., NGC 6522 has a slight amount of resolution toward its edges while NGC 6528 appears more random.
Both NGC 6522 and NGC 6528 were discovered by Sir William Herschel on the same night 1784 and both are the same distance from the galaxy’s nucleus. But there the similarities end: NGC 6522 has an intermediate metallicity. At its core, the red giants have been depleted – stripped tidally by evolving blue stragglers. It is possible that core collapse has already occurred. NGC 6528, however, contains one of the highest metal contents of any known globular cluster collected in its bulging core!
Now, let’s go kill our night vision and have a look at Jupiter! During the course of the evening of July 26-27, several events will happen – including eclipses and transits. For viewers in the United States eastern time zone, look for the Great Red Spot to appear on the meridian at around 10:48 p.m. While it’s difficult to make out the faint contrast of this most popular of all jovian features, take the opportunity to experiment with color filters if you have them. Even wearing sunglasses can sometimes produce surprising results!
Sunday, July 27 – Today in 1892, a very special astronomer was born – Sir George Biddell Airy. Does that name sound familiar? Anyone who uses a refractor understands the properties of the “Airy disc” as first outlined in his paper “On the Diffraction of an Object-Glass with Circular Aperture.” But, Sir George achieved a bit more: As Astronomer Royal from 1835 to 1881, his tireless devotion to planetary study led to the discovery by P. A. Hansen of two new irregularities in the moon’s motion. Not enough? Airy’s calculations also determined the mean density of the Earth. More? Then thank Sir George for giving us Greenwich Mean Time!
Are you still having no luck in finding a deep-space object? Then how about one that’s simple to locate for all optics. All you have to know is Antares and go west…
As one of the loosest globular clusters, M4 would be tremendous if we were not looking at it through a heavy cloud of interstellar dust. To binoculars, it is easy to pick out a very round, diffuse patch – yet it will begin resolution with even a small telescope. Large telescopes will also easily see a central “bar” of stellar concentration across M4’s core region, which was first noted by Herschel.
As an object of scientific study, the first millisecond pulsar was discovered within M4 in 1987 – one which spins 10 times faster than the Crab Nebula pulsar. Photographed by the Hubble Space Telescope in 1995, M4 was found to contain white dwarf stars – the oldest in our galaxy – with a planet orbiting one of them! A little more than twice the size of Jupiter, this planet is believed to be as old as the cluster itself. At 13 billion years, it would be three times the age of the Sol system!
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This story has been spreading like wildfire across the internet, as well as other news sources, which is not surprising given the topic. In a radio interview in the UK, and in a subsequent article in the Daily Register, former Apollo astronaut Edgar Mitchell said he believes there is life on other planets. OK, that’s not much of a bombshell. But then he went on to say that aliens have visited Earth, and our governments have been covering it up. That was the shocker. Mitchell said he was “privileged enough to be in on the fact that we’ve been visited on this planet and the U.F.O. phenomena is real.” While he didn’t offer any real facts or say that he has actually seen aliens, he said big organizations will soon be offering full disclosure. NASA officials responded to Mitchell’s comments fairly politely with this comment: “NASA does not track UFOs. NASA is not involved in any sort of cover up about alien life on this planet or anywhere in the universe. Dr. Mitchell is a great American, but we do not share his opinions on this issue.”
Mitchell was a member of Apollo 14, and was the sixth man to walk on the moon. While he didn’t offer any real proof of his claims, he does seemingly have credentials. However, he alone among the Apollo astronauts makes these types of claims, and has been saying things like this for quite some time. He said on the way home from the moon he had a “transformational, transcendental experience.” After his flight he started the Institute of Noetic Sciences, which “conducts and sponsors leading-edge research into the potentials and powers of consciousness.”
There was another interesting statement by Mitchell during this interview: “There’s more nonsense out there about this than there is real knowledge.”
Of course, the UFO folks have glommed onto these latest statements by Mitchell, but here’s what some of the more reputable news sites have been saying:
New York Times Blog: “While Mr. Mitchell, 77, is certainly entitled to his own views on the issue, the rest of us may need to wait for something more convincing.”
Huffington Post: “Mitchell, a member of the Apollo 14 team, has long held these beliefs despite the fact that he himself has never seen neither an alien or a U.F.O.”
NASA Watch’s Keith Cowing: “I assume you have proof to back up your extraterrestrial conspiracy mongering, Ed.”
Robert Pearlman, the editor of CollectSpace, wrote the following on an online forum:
Based on the nine minute call, it (a) doesn’t seem to be anything tremendously different from prior comments and writings by Dr. Mitchell, and (b) he isn’t actually claiming first-hand knowledge but rather repeating what he was told by others. It is no secret that Dr. Mitchell’s Noetic Science Institute attracts those that believe in extraterrestrials and that he has attended numerous conferences where they have been on the agenda for discussion, thus what he says here is of little surprise (and some might argue, consequence).
Irene Klotz from Discovery interviewed Mitchell after his UK radio interview and here’s an excerpt:
Irene Klotz: I wanted to ask you if there was anything about the radio interview you did that was different from what you’ve said in the past.
Edgar Mitchell: No, there’s nothing different. Several of (the reports of the interview) that I’ve seen come around have some flaws in them. Some of the reports pushed it or spun it incorrectly. NASA had nothing to do with anything I’ve done. I wasn’t briefed by NASA. There haven’t been any sightings as a result of my flight service there, so if that part of it comes out on anything you’ve seen it is just totally wrong.
In this Discovery interview, and in previous interviews, Mitchell has not offered any definite proof of his claims, and said he’s only been “told by people who were utterly sworn to secrecy” about alien visits to Earth. Mitchell grew up in Roswell, New Mexico.
All in all, unless Mitchell can offer definitive proof, his claims will have to be put in the same class as anyone else that makes similar claims, despite his background. Even with the prevalence of cameras and video cameras among the general public and with an abundance of investigative news reporters out there (all wanting to break the news story of the millennium) still, no one has been able to produce credible proof of aliens visiting Earth.
As the Bad Astronomer Phil Plait has said repeatedly, the people constantly looking at the skies, professional and amateur astronomers, have made no claims of UFO’s or aliens visiting Earth. They know what they are looking at in the sky.
For a dose of reality, please see Phil’s take on UFO’s.
Take a very close look at this image of NGC 5216 and companion galaxy NGC 5218 and you’ll see a bridge of galactic material that joins these two isolated galaxies. Located in the constellation of Ursa Major (RA 12 30 30 Dec +62 59), this tidally connected pair known as Keenan’s System has been well-studied but you’ll find they have rarely been imaged.
First discovered by Friedrich Wilhelm Herschel in 1790 and later studied as Intergalactic Nebulae in 1926 by Edwin Hubble, it wasn’t until 1935 until PC Keenan noted this double galaxy mystery seemed to be connected by “luminous debris” – a connection that spans 22,000 light years. Keenan noted the peculiar structure in his paper but it would be 1958 before the bridge of material was “rediscovered” by observers at Lick and Palomar observatories in “The Interaction of Galaxies and the Nature of Their Arms, Spanning Filaments and Tails”.
By 1966, peculiar type spiral NGC 5216 and the globular galaxy NGC 5218 were included as Arp 104 into Halton Arp’s Catalog of Peculiar Galaxies and the 17.3 million light year distant pair were beginning to capture the attention they deserved. Studies were conducted of active galactic nuclei among interacting galaxies and galaxies with extreme tidal distortions and it wasn’t long before science realized these two galaxies had collided – stripping stars, gas and dust from each other which appear about them like skewed halos. Once interaction has occurred, the bridge between them fills with “stars in new and perturbed orbits”.
In infrared studies done by Bushouse (et al), even more fascinating details have been revealed as we learn that galaxy-to-galaxy collisions can produce higher infrared emissions. “Only the most strongly interacting systems in the sample show extreme values of infrared excess, suggesting that deep, interpenetrating collisions are necessary to drive infrared emission to extreme levels. Comparisons with optical indicators of star formation show that infrared excess and color temperatures correlate with the level of star-formation activity in the interacting galaxies. All interacting galaxies in our sample that exhibit an infrared excess and have higher than normal color temperatures also have optical indicators of high levels of star formation. It is not necessary to invoke processes other than star formation to account for the enhanced infrared luminosity in this sample of interacting galaxies.”
What’s happening between the pair is causing starburst activity, perhaps from the sharing of gases. According to Casaola (et al); “From the data it appears that interacting galaxies have a higher gas content than normal ones. Galaxies classified as ellipticals have both a dust and gas content one order of magnitude higher than normal. Spirals have in most part a normal dust and HI content but an higher molecular gas mass. The X-ray luminosity also appears higher than that of normal galaxies of same morphological type, both including or excluding AGNs. We considered the alternative possibilities that the molecular gas excess may derive from the existence of tidal torques which produce gas infall from the surrounding regions… it appears that interacting galaxies possess a higher molecular mass than normal galaxies but with a similar star formation efficiency.”
However, the single most interesting point is the remarkable filament which connects NGC 5216 and companion galaxy NGC 5218 – a “concentrated string-like formation connecting the two systems and the fingerlike extension, or countertide, protruding from the globular cluster NGC 518 and starting on the same tangent as the interconnecting filament.” It was this very string of material which has been a very recent study of Beverly Smith (et al) in the Spitzer infrared, Galaxy Evolution Explorer UV, Sloan Digitized Sky Survey and Southeastern Association for Research in Astronomy. Their studies helped to reveal these “beads on a string”: a series of star-formation complexes. According to their findings; “Our model suggests that bridge material falling into the potential of the companion overshoots the companion. The gas then piles up at apogalacticon before falling back onto the companion, and star formation occurs in the pile-up.”
The light data for this awesome image was gathered by AORAIA member Martin Winder and processed by Dr. Dietmar Hager. This particular image took nearly 10 hours of exposure time and untold hours of processing to turn it into the beautiful, study-grade photo you see here. We thank Mr. Winder and Dr. Hager for sharing this exclusive photo with us!
Solar System Simulator – It’s not really a game, but the Solar System simulator from NASA is one of the coolest online tools you’ll find. It lets you simulate the entire Solar System, so you can see what things look like from any planet, moon or spaceship. Very cool.
Solar System Jigsaw – This interactive tool from BBC lets you build jigsaw puzzles on the Internet of the Solar System. You can make them more difficult or easy.
Solar System Games – Windows on the Universe has a whole system of Solar System games you can try out. Some are built in Java, and others are programmed in Macromedia Flash, so you might need to install plugins to make them work.
Science@NASA – NASA’s science website for kids has a series of games you can play online. You can explore Mars, or compare the size of planets.
NASA Space Place – NASA has many sites for kids, and most of these have online games you can play. This Solar System game lets you see how well you know your moons and planets.
Surfing the Solar System – This game from the Astronomical Society of the Pacific lets you go on a treasure hunt through the Solar System.
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The Solar System holds some big records. Want to know which are the largest in the Solar System?
Largest star
Well, there’s only one star in the Solar System: the Sun, so it’s the automatic winner here. The Sun measures 1.4 million km across. That’s so big, you could put 109 Earths side by side to match the size of the Sun. Astronomers have theorized that the Sun might have a companion star on a long orbit, but if was anywhere as large or bright as the Sun, we’d definitely see it. So this is a record that won’t fall.
Largest Planet
The largest planet in the Solar System is Jupiter, which measures 143,000 km across its equator. That’s the same as 11 Earths. In fact, Jupiter is so large that it has 2.5 times the mass of all the other planets in the Solar System… combined. One interesting note is the Jupiter actually can’t get any bigger. If you added more mass to Jupiter, the increased gravity would actually pull it together harder, and it would shrink.
Largest Moon
The largest moon in the Solar System is Jupiter’s moon Ganymede, which measures 5,268 km across. It’s actually larger than Mercury, as well as Pluto and the dwarf planets. If it orbited the Sun, it might be a planet in its own right. Astronomers used to think that Saturn’s moon Titan was the largest moon, but then they realized that Titan’s thick atmosphere made it just appear larger.
Largest Mountain
The largest mountain in the Solar System is Olympus Mons on Mars. This ancient shield volcano measures 27 km tall. That makes it 3 times the elevation of Mount Everest on Earth, and 2.6 times the height of Mauna Kea from its base below the ocean. Astronomers think that Olympus Mons got so big because Mars never developed plate tectonics. A hotspot opened up to the surface of Mars, and just stayed there for billions of years, pouring out lava and building up the mountain. Olympus Mons is also the largest volcano in the Solar System.
Largest Asteroid
The largest object in the asteroid belt is Ceres, measuring 974 km across. But there’s a problem, Ceres has been upgraded to the status of a dwarf planet, like Pluto. This means that the largest actual asteroid is Vesta, also located in the asteroid belt. Vesta measures 530 km across, and contains about 9% of the mass of the asteroid belt.
Largest Crater
The largest crater in the Solar System is on the Moon. It’s called the South Pole-Aitken Basin, and measures about 2,500 km across. Astronomers on Earth didn’t realize it was a huge crater until the first spacecraft orbited the Moon. That’s because we can’t see the crater itself from our vantage point, just a huge rim of mountains. South Pole-Aitken Basin might actually be the second biggest crater in the Solar System. That’s because new research indicates that a much larger impact site might be on Mars, called the Borealis Basin – measuring 8,500 km across, but more proof needs to be gathered.
Project Lucifer. Could the plutonium fuel onboard the Cassini mission cause a nuclear chain reaction on Saturn? Credit: NASA/US Department of Defense
[/caption] The story: On October 15th 1997, the Cassini-Huygens mission blasted off from Cape Canaveral Air Force Station to explore Saturn and its moons. It continues to study the ringed gas giant today and its mission has been extended till 2010. Cassini is is powered by 32.8 kg (72 lbs) of plutonium fuel. A radioactive power source is the only option for missions travelling beyond the orbit of Mars as sunlight is too weak for solar panels to be effective. However, NASA (in association with secret organizations, such as the Illuminati or the Freemasons) wants to use this plutonium for a “higher purpose”, dropping Cassini deep into Saturn at the end of its mission where atmospheric pressures will be so large that it will compress the probe, detonating like a nuclear bomb. What’s more, this will trigger a chain reaction, kick-starting nuclear fusion, turning Saturn into a fireball. This is what has become known as The Lucifer Project. This second sun will have dire consequences for us on Earth, killing millions from the huge influx of radiation by this newborn star. Earth’s loss becomes the Saturn moon Titan’s gain, suddenly it is habitable and the organizations playing “God” can start a new civilization in the Saturn system. What’s more, exactly the same thing was attempted when the Galileo probe was dropped into Jupiter’s atmosphere in 2003…
The reality: Now that the Cassini mission has been extended by two years, we can expect this conspiracy theory to become more and more vocal in the coming months. But like the Galileo/Jupiter/second sun theory, this one is just as inaccurate, once again using bad science to scare people (much like Planet X then)…
So what happened when Galileo dropped into Jupiter? Galileo undergoing preparations before launch in 1989. Credit: NASA
Well… nothing really.
In 2003, NASA took the prudent decision to terminate the hugely successful Galileo mission by using its last drops of propellent to push it at high speed into the gas giant. By doing so, this ensured the probe would burn up during re-entry, dispersing and burning any contaminants (such as terrestrial bacteria and the radioactive plutonium-238 fuel on board). The primary concern about letting Galileo sit in a graveyard orbit was that if mission control lost contact (very likely as the radiation belts surrounding Jupiter were degrading the probe’s ageing electronics), there may have been the possibility that Galileo would crash into one of the Jovian moons, contaminating them and killing any possible extra-terrestrial microbial life. This was a serious concern, especially in the case of Europa which could be a prime location for life to thrive below its ice-encrusted surface.
Now this is where the intrigue begins. Long before Galileo plummeted into Jupiter’s atmosphere, conspiracy theorists cited that NASA wanted to create an explosion within the body of the gas giant, thus igniting a chain reaction, creating a second sun (Jupiter is often called a ‘failed star’, although it has always been way too small to support nuclear reactions in its core). This was proven wrong on many counts, but there were three main reasons why this could not happen:
The design of the radioisotope thermoelectric generators (RTGs) supplying energy to the craft wouldn’t allow it.
The physics behind a nuclear explosion (nuclear fission) wouldn’t allow it.
The physics of how a star works (nuclear fusion) wouldn’t allow it.
Five years after the Galileo impact, Jupiter still looks to be in fine health (and it certainly isn’t close to being a star). Although history has already proven you can’t create a star from a gas giant using a space probe (i.e. Jupiter + Probe ≠ Star), conspiracy theorists think that NASA’s evil plan failed and there is some evidence that something did happen after Galileo got swallowed by Jupiter (and that NASA is pinning their hopes on the Cassini/Saturn combo).
Cue the Big Black Spot
The mystery black spot in 2003 (by Eric Ng) compared with one of the Shoemaker-Levy 9 fragments impact sites in 1994 (NASA)
Backing up the conspiracy theorists’ claims that there was an explosion inside the Jovian atmosphere after Galileo hit was the discovery of a dark blob near the equator of Jupiter a month after the event. This was widely reported across the web, but only a couple of observations were made before it disappeared. Some explanations pointed out that the blob could have been a short-lived dynamic atmospheric feature or it was a shadow from one of the Jovian moons. After this initial excitement, nothing else surfaced about the phenomenon. However, some were keen to point out that the dark patch on Jupiter’s surface may have been a manifestation of a nuclear detonation from Galileo deep within the planet which, after a month, eventually floated to the surface. Comparisons had even made with the 1994 features generated by the impact of the pieces of Comet Shoemaker-Levy 9 (pictured above).
What ever the cause of this dark feature, it didn’t come from Galileo as a nuclear detonation simply was not possible. What’s more, a nuclear detonation from the Cassini mission when it enters Saturn’s atmosphere in 2010 is also impossible, and here’s why…
The Radioisotope Thermoelectric Generators (RTGs) The Cassini RTG, one of three on board. Credit: NASA
RTGs are a tried and tested technology in use since the 1960’s. Various RTG designs have been used on a huge number of missions including Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, Galileo, Ulysses, Cassini and, most recently, New Horizons. RTGs are a very dependable source of power for space missions where solar panels have not been an option. For Cassini, if solar panels were used, they would need to have a huge area to collect the meagre sunlight at 10 AU, thus impractical to launch and operate.
The three RTGs on board Cassini are fuelled by small pellets of plutonium-238 (238Pu) encased separately in shock-proof containers known as general purpose heat source modules. There are 18 modules in each RTG. Through the use of thermocouples, the steady heat generated by the radioactive decay of the plutonium isotope is converted into electricity to supply Cassini. It is worth noting at this point that 238Pu is not weapon grade (i.e. it is very difficult to generate nuclear fission, 239Pu is more suited for this purpose). There are also dozens of Radioisotope Heater Units (RHUs) on board Cassini that provide a steady heat to critical subsystems, which contain single pellets of Pu-238. Again, these units are separated and shielded, each weighing 40 grams. For more details on this, check out the NASA Factsheet: Spacecraft Power for Cassini.
Inside an RHU and RTG (Roland Piquepaille)
Shielding is critical for each plutonium pellet, primarily to prevent radioactive contamination during launch of space missions. Should there be an incident during launch, space agencies such as NASA must assure the containment of the radioactive material. Therefore all RTGs and RHUs are completely safe regardless of the stresses they are put under.
So, like Galileo, Cassini will hit Saturn’s atmosphere at a high velocity (Galileo hit the Jovian atmosphere at a speed of 50 km/s) and disintegrate very quickly before burning to a cinder. The point I want to highlight here is that Cassini will break apart like any fast-moving object during re-entry.
Still, conspiracy theorists are quick to point out that Cassini is carrying a huge amount of plutonium, totalling 32.8 kg (even though it is not the weapon-grade 239Pu and all the bits of 238Pu are tiny pellets, encased in damage-proof containers, being scattered through Saturn’s atmosphere). But ignoring all the logical arguments against, it will still generate a nuclear explosion, right?
Alas, no.
So how does a nuclear bomb work anyway?
Artist impression of Galileo burning up when falling into the Jovian atmosphere. Credit: David A Hardy
For a general run-down of the basics behind a nuclear weapon, check out the very clear description at How Stuff Works: How Nuclear Bombs Work (scroll down to “Implosion-Triggered Fission Bomb,” as this is what the conspiracy theorists believe Cassini will emulate).
So there’s Cassini, plummeting through Saturn’s atmosphere in two years time. As it gets deeper, bits fall off and burnt by the friction caused by re-entry. When I say fall off, I mean they are no longer attached. For a nuclear detonation to occur we need a solid mass of weapon grade plutonium. By solid mass, I mean we need a minimum amount of the stuff for nuclear fission to occur (a.k.a. “critical mass”). The critical mass of 238Pu is approximately 10 kg (US DoE publication), so Cassini has enough 238Pu for three crude nuclear bombs (ignoring the fact that it is very difficult to build a 238Pu weapon in the first place). But how could all those tiny pellets of 238Pu be pulled together, in free-fall, casings removed, letting the pressure of Saturn’s atmosphere force it all together tipping it toward critical mass? Is that really possible? No.
An imploding nuclear weapon (answers.com)
Even if by some chance all the 238Pu in one RTG melded together, how would it detonate? For detonation of an implosion-triggered fission bomb to occur, sub-critical masses need to be forced together at the same instant. The only way this is possible is to surround the sub-critical masses with high-explosives so a shock wave rapidly collapses the sub-critical masses together. Only then may a chain reaction be sustained. Unless NASA has been really sneaky and hidden some explosives inside their RTGs, detonation is not possible. Using atmospheric pressure alone is not a viable explanation.
Now we can see that it is pretty much impossible for the plutonium on board Cassini to create a nuclear explosion. But if there was a nuclear detonation, could a chain reaction occur? Could Saturn become a star?
Mars' Midnight Sun. Credit: NASA/JPL-Caltech/U of Arizona/Texas A&M University
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This panorama mosaic of images was taken by the Surface Stereo Imager on board NASA’s Phoenix Mars Lander. This mosaic documents the midnight sun during several days of the mission, from Sol 46, or the 46th day of the mission to Sol 56 (that would be to July 12 – 22, 2008 here on Earth.) The foreground and sky images were taken on Sol 54, when the lander pulled an all-nighter to coordinate work with the Mars Reconnaissance Orbiter. The solar images were taken between 10 p.m. and 2 a.m., local solar time, on the different nights of the 11 sol period. During this period, the sun’s path got slightly lower over the northern horizon, causing the lack of smoothness to the curve. This pan captures the polar nature of the Phoenix mission in its similarity to time lapse pictures taken above the Arctic Circle on Earth.
The latest activities of the lander has brought it closer to analyzing a sample of icy soil in the TEGA oven.
On Tuesday and Wednesday, Phoenix used its robotic arm to scrape the top of the hard layer in the trench called “Snow White.”
“We are monitoring changes between the scrapes,” said Doug Ming of NASA Johnson Space Center. “It appears that there is fairly rapid sublimation of some of the ice after scraping exposes fresh material, leaving a thin layer of soil particles that had been mixed with the ice. There’s a color change from darker to bluer to redder. We want to characterize that on Sol 58 to know what to expect when we scrape just before collecting the next sample.”
The science team is preparing to quickly collect a sample from the hard layer of Snow White and deliver it to one of the eight ovens of Phoenix’s Thermal and Evolved-Gas Analyzer (TEGA). Doors to the oven have been opened to receive the sample. TEGA will “bake and sniff” the samples to analyze the composition of the soil and ice.
On Wednesday the team also checked out the heater on TEGA is working properly, to verify that pressure sensors can be warmed enough to operate properly early in the Mars morning.
“For the next sample, we will be operating the instrument earlier in the morning than we have before,” said William Boynton of the University of Arizona, lead scientist for TEGA. “It will be almost the coldest part of the day, because we want to collect the sample cold and deliver it cold.”
On the day when Phoenix will deliver the next sample to TEGA, the team plans to have lander activities begin about three hours earlier than the usual start time of about 9 a.m. local solar time.
On Thursday, one set of imaging commands will check a northwestern portion of the horizon repeatedly during early afternoon to see whether any dust devils can be seen. This will be the first systematic check by Phoenix for dust devils. The Mars Rover Spirit was able to image sequences of dust devils in its location, south of Mars’ equator.
