Comet Fights with the Sun. Loses.

The comet death dive (NASA/ESA/SOHO).

The comet death dive (NASA/ESA/SOHO).

What happens when you put a snowball in front of an open fireplace? It melts. What happens when you throw a comet at the Sun? Erm… it doesn’t end well. In fact, as this daredevil comet proves, comets get vapourized very quickly. And the Solar and Heliospheric Observatory (SOHO) captured the whole event, here’s a video.

Sungrazing comets are spotted fairly regularly and this particular comet spotted over the weekend is likely a member of the Kreutz sungrazer family. This group of comets are thought to have been spawned when a giant comet broke up over 2000 years ago. However, the larger Kreutz fragments usually make a close approach to the Sun 3 or 4 times a year, but there have been 3 such events in 2010 so far.

As noted by Spaceweather.com, this could just be a statistical anomaly, but it could be that these fragments are a part of a swarm of comets approaching perihelion (closest approach to the Sun).

Either way, if you’re a comet, don’t venture too close to the Sun, you might get eaten.

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P/2010 A2 Was An Asteroid Collision (Says Hubble)

What you see here is something mankind has never seen before, the aftermath of an asteroid collision. This conclusion comes after the Hubble Space Telescope was commanded to take a closer look at a strange comet-like object pottering around in the asteroid belt between the orbits of Mars and Jupiter.

The truth is we’re still struggling to understand what this means,” said David Jewitt, a planetary physicist from UCLA. “It’s most likely the result of a recent collision between two asteroids.”

After P/2010 A2 was discovered in January, Jewitt managed to get observation time on Hubble to get a closer look of what was thought could be a rare asteroid-comet hybrid.

In the image, the object named P/2010 A2 has a very obvious “X” on its surface shaped pattern in its tale, possibly the location where a smaller body slammed into it at high speed. The result of this hyper-velocity impact produced a lot of debris and scientists think the comet-like tail being swept back by the pressure of the solar wind is dust and outgassing volatiles (like subliming water ice).

Although this kind of event has never been observed before, over the lifetime of the evolving solar system, events like this occur on a regular basis, in fact asteroid collisions have shaped the asteroid belt. Interestingly, it is thought this impact was caused by a collision of a “Flora family” asteroid, a type of object that may have wiped out the dinosaurs 65 million years ago. (Don’t worry, this collision won’t affect Earth in any way, the dinosaur thing is simply an interesting connection!)

What an incredible discovery, it’s fortunate that we have Hubble’s excellent eyesight to peer deep into the asteroid belt…

Sources: Reuters, Discovery News

Could P/2010 A2 be the First Ever Observation of an Asteroid Collision?

Something rather bizarre was observed in the asteroid belt on January 6. Ray Villard at Discovery News has just posted an exciting article about the discovery of a comet… but it’s not your average, run-of-the-mill kinda comet. This comet appears to orbit the Sun, embedded in the asteroid belt.

Comets don’t usually do that, they tend to have elliptical and inclined orbits, orbits that carry them close to the Sun (when they start to heat up, creating an attractive cometary tail as volatile ices sublimate into space, producing a dusty vapor). They are then flung back out into the furthest reaches of the Solar System where the heating stops and the comet tail disappears until the next solar approach.

But P/2010 A2 — discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey — has a circular orbit and it still appears to be venting something into space.

P/2010 A2 (LINEAR): A comet or asteroid debris? (Spacewatch/U of Arizona)

There is the possibility that it is a member of a very exclusive bunch of objects known as main belt comets (MBCs). MBCs are confused asteroid/comet hybrids that appear to spontaneously vent vapor and dust into space and yet stay confined to the asteroid belt. But, if P/2010 A2 is confirmed to be one of these, it will only be the fifth such object to be discovered.

So what else could it be? If the potential discovery of an MBC doesn’t excite you enough, it could be something else entirely: the dust produced by a hyper-velocity impact between two asteroids. If this is the case, it would be the first ever observation of an asteroid impact in the Solar System.

The asteroid belt isn’t the same asteroid belt you might see in science fiction; although there are countless rocky bodies in our asteroid belt, it is rare that these rocky bodies encounter each other. Space is very big, and although the density of asteroids in this region might be considered to be “high”, this is space we’re talking about, you can fly a spaceship through the region without having to worry that you’ll bump into something. The average distance between asteroids is huge, making it a very rare occurrence any two should hit. But given enough asteroids, and enough time, eventually asteroid collisions do happen. And in the case of P/2010 A2, we might have been lucky.

Asteroid collisions: Rare, but possible.

Asteroid collisions: Rare, but possible.

The chatter between comet/asteroid experts is increasing, and on one message board posting, Javier Licandro (Instituto de Astrofísica de Canarias, Spain) reports observing a secondary asteroid traveling with the cloud-like P/2010 A2.

The asteroid moves in the same direction and at the same rate as the comet,” reports Licandro on The Minor Planet Mailing List. “In addition, the P/2010 A2 (LINEAR) image does not show any central condensation and looks like a ‘dust swarm’.”

A short lived event, such as a collision, may have produced the observed dust ejecta.”

Therefore, this ‘comet’ may actually be the debris that was ejected after a collision between two asteroids. Although these are preliminary findings and it’s going to take some serious observing time to understand the true nature of P/2010 A2, it’s exciting to think that we may just have observed an incredibly rare event, 250 million miles away.

Source: Discovery News

Tethys Plays Hide and Seek with Cassini

Which planet does Tethys orbit again?

I do admit, I’m terrible with names, but I never forget a face. In this case, the face I didn’t forget was a little moon orbiting Saturn (it’s the one that looks like the Death Star from Star Wars). However, after seeing this photo, I doubt I’ll ever forget Tethys’ name again.

In a photo snapped by the awesome Cassini Equinox mission back in November, the little moon with characteristic impact crater carved into its crust can be seen to be drifting behind Titan. Tethys only disappears for 18 minutes behind Titan’s thick atmosphere, but it was enough to ignite my interest in the icy world.

It’s strange how a simple photograph and perfect timing can ignite the imagination, as I doubt “just another moon shot” would have the same effect. No, this is a moon drifting in front of another moon as seen by a veteran spaceship orbiting the second largest planet in the solar system millions of miles away. Sometimes words are insufficient to describe the enormity of what we are doing in space.

So, sod the words and look at this, you won’t be disappointed:

And 18 minutes later:

Lovely.

Source and full-res images: NASA, Discovery News

Much Ado About Apophis

Concept art for the ESA Don Quijote asteroid mission concept (ESA)

Concept art for the ESA Don Quijote asteroid mission (ESA)

Apophis is a 300 meter wide asteroid that caused a stir back in 2004. When NASA discovered the near-Earth asteroid (or NEO), it appeared to be tumbling in our direction Armageddon-style and the initial odds for a 2029 impact were 1-in-37. Understandably, people got scared, the media went nuts and astrophysicists were suddenly very interested in space rock deflection techniques.

Fortunately for us, NASA has downgraded the threat to a zero (note zero) chance of Apophis bumping into us in 2029, and lowered the risk of a follow-up impact in 2036 from a 1-in-45,000 chance to a 1-in-250,000 chance.

It’s important to note that NASA didn’t just pull these numbers out of a hat; the space agency has been tracking Apophis intently since its discovery, plotted its position and projected its location to a very high degree of precision. The more we watch Apophis, the more the world’s scientists are convinced that the asteroid poses a very tiny risk to life on Earth. In fact, giving anything a 1-in-250,000 chance of happening is more of a courtesy than a ‘risk.’ Granted, we’re talking about a global catastrophe should Apophis hit, but would you ever bet on those kinds of odds?

Apparently, the Russian space agency thinks it’s more of a game of Russian Roulette than NASA thinks.

I don’t remember exactly, but it seems to me it could hit the Earth by 2032,” said Anatoly Perminov, the head of Roscosmos, on December 30, 2009. “People’s lives are at stake. We should pay several hundred million dollars and build a system that would allow to prevent a collision, rather than sit and wait for it to happen and kill hundreds of thousands of people.”

What are the legal implications of asteroid deflection? Read: Space Experts to Discuss Threat of Asteroid Impact

Wait a minute. Does Perminov know something NASA doesn’t? Is he even referring to Apophis? You know, the same asteroid NASA has calculated that has a cat in hell’s chance of causing bother in 2036? And what’s this about the year 2032?

Just for the record, Perminov is indeed referring to Apophis, but he got the date wrong (Apophis does not make a flyby in 2032). Perminov also puts a price on saving hundreds of thousands of people… “several hundred million dollars” should do it, apparently.

On the one hand I’m impressed that Roscosmos is calling for some kind of anti-asteroid shield, but on the other, Perminov’s concern is terribly misplaced (and potentially damaging). His statement sounds as if he’s only just heard about Apophis and then thrown into a press conference unprepared, then asked what he’s going to do about this impending doom. Naturally, in that situation he would have blurted out the first thing that popped into his head: We need to save the world! However, this isn’t the first time he’d heard about Apophis.

Boris Shustov, the director of the Institute of Astronomy under the Russian Academy of Sciences, tried to repair the damage pointing out that Perminov was just using Apophis as a “symbolic example, there are many other dangerous objects we know little about.”

However, saving the world from a theoretical “dangerous object” that may or may not hit us for the next few hundred/thousand/million years is less likely to get funding that an imminent 2032… sorry, 2036 impact.

Although Perminov might sound reasonable in asking for asteroid deflection funding, using sensationalist means to try to leverage funding only serves to make the same funding hard to come by.

In the AGU 2009 meeting in San Fransisco last month, ex-Apollo astronaut Rusty Schweickart outlined his organization’s plans to deflect an asteroid should it pose a threat to Earth. The B612 Foundation points out that there is a ~2% chance of Earth being involved with an “unacceptable” collision in the next century (not by Apophis, but by another undiscovered asteroid), but Schweickart and his colleagues want to emphasize urgency, not panic.

An infrastructure needs to be put in place to deal with asteroid deflection, but this goal will only be hindered by unwarranted alarm by the likes of Perminov. Asteroid detection and deflection will be two critical skills mankind will need to develop for the long-term survival of life on Earth, but the head of Roscosmos is running the risk of making the issue sound more like a crazed rant than anything of substance.

Besides, when Perminov says, “Everything will be done according to the laws of physics,” perhaps he shouldn’t be in charge of messing around with the orbits of NEOs after all…

What Will It Take To Blow Up Pluto?

“25 billion of your biggest bombs please. I’ll pay credit, thanks!”

"I love the smell of venting volatiles in the morning..."

"I love the smell of venting volatiles in the morning..."

The Pluto debate frustrates me, as you may have noticed. It’s not that I have particularly strong views about whether it should be called a planet or a dwarf planet or a plutoid or pygmy planetoid, it’s that I really don’t care; I actually see Pluto’s “demotion” as exciting progress in the field of Solar System science rather than any derogatory gesture aimed at Pluto. Pluto is still Pluto; it hasn’t been knocked out of orbit, it hasn’t even been “bombed” (unlike our poor old Moon), it’s just being filed under a different category.

A King Amongst Dwarfs

In my opinion, calling Pluto a “planet” was unworkable, especially after a bigger dwarf planet was discovered in 2005 by a team of astronomers led by Dr. Mike Brown. This dwarf planet was named Eris (or 136199 Eris) and at first it seemed like we had gained a tenth planet.

The “ten planets” thing was short lived, however. In recognition that Eris probably represented the beginning of a spate of discoveries of welterweight worlds, the International Astronomical Union (IAU) took a vote in 2006 and decided to redefine what constitutes a planet. Pluto was in the firing line, became a rounding error and was dropped from the planetary club.

Kicked out and nowhere to go.

Kicked out and nowhere to go.

But it wasn’t all bad for the little guy. Pluto was designated king of all “plutoids” (trans-Neptunian dwarf planets) in 2008, meaning another three dwarf planets now orbited the Sun with this designation (Eris, Haumea, and Makemake in addition to Pluto).

In a previous Astroengine article, I made the point (and I’m going to quote myself because I can):

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.

I haven’t really thought much about this statement until, today, @PlutoKiller himself (Mike Brown) tweeted, “Seriously, what just happened? The entire discussion is on placing explosives in the solar system. Pluto has not even been mentioned.” I then fired off a reply saying something about building a New Horizons 2 and packing it with plutonium to which @PlutoKiller said, Evil Santa-style: “Just in time for Xmas.”

And then the penny dropped.

Kuiper Belt Cruelness

To be honest, I’m astonished I haven’t thought of this before. Looking at Mike’s Twitter feed should have been enough inspiration, but until I wondered down the bombing Pluto => plutonium enrichment => lets fly a shedload of plutonium to Pluto path, that I asked the question: How much energy is needed to completely destroy Pluto?

Now we’re talking! Time for some Kuiper belt mayhem!

It might seem quiet now...

It might seem quiet now...

I’m not talking about simply bombing Pluto and making a big crater, I’m not even talking about fire bombing all the volatiles out of its frozen surface, I want to remove Pluto from existence. Why do I want to do this? Well, for fun, and because @PlutoKiller himself said so. And it’s Halloween, so why not?

So how much energy is required to do this?

For this gargantuan task, I cheated and looked up the method used by Matt Springer over at Built on Facts to derive how much energy was required by the Star Wars Death Star to shred Earth. In that case, 2.2 × 1032 Joules was needed to totally erase our planet (that’s a week’s-worth of solar output). That’s a lot, right?

Plutoid Killing Equation

Now, energy is energy and mass is mass, let’s give Pluto the same treatment. Using the following equation (known henceforth as the “Plutoid Killing Equation”, or simply PluKE), we can find out how much energy we need to erase Pluto:

The equation that can turn a dwarf planet into dust, as derived by Matt Springer.

This equation is the total gravitational binding energy of a sphere of mass, M and radius, R. G is the Gravitational Constant. For Pluto, a sphere, its vital statistics are:

MPluto = 1.305 × 1022 kg

RPluto = 1.153 × 106 m

and

G = 6.673 × 10-11 m3 kg-1 s-2

Plugging the numbers into PluKE, we can derive the total energy required to kill Pluto, literally:

EPluto(dead) = 5.914×1027 Joules

Oops, who put those WMDs there?

Oops, who put those WMDs there?

But what does this number mean? This is the bare minimum energy required to match the gravitational binding energy of Pluto. If you want to rip the dwarf planet apart (plus pyrotechnics and speeding debris), you’ll need a lot more energy. However, nearly 6×1027 Joules (that’s a 6 followed by 27 zeros) delivered into Pluto in one second should give the little world a very bad day.

Tsar Very Much

But how can we “deliver” this vast quantity of energy in one second? I suspect that any super-advanced civilization hell-bent of wiping out planets will have a better idea of this than me, but using weapons that are available to modern man might be a good place to start. Forget the uber-powerful death ray emitted by the Death Star, that’s sci-fi. It may not be sci-fact, but how about sending some nuclear bombs to the Kuiper belt?

How many bombs will we need? Ten? Ten dozen? A thousand?

The most powerful nuclear weapon tested was the Soviet 58 MT Tsar Bomba in 1961. So if we know how much energy is released by one of those beasts, we should be able to work out how many we’ll need to send to the unsuspecting Pluto.

1 MT = 1 megaton of TNT = 4.184×1015 Joules

therefore, a single Tsar Bomba has the potential to release an energy of:

58 MT = 58 × 4.184×1015 Joules = 2.427×1017 Joules

We needed 6×1027 Joules to wipe out Pluto, obviously the 2.4×1017 Joules a single bomb can deliver is woefully short of our goal. So how many Tsar Bomba weapons do we need?

(6×1027 Joules) / (2.4×1017 Joules) = 2.5×1010

We need to build 25,000,000,000 nuclear bombs. 25 billion. Ouch.

Obviously, looking at this estimation, it is impossible to destroy a dwarf planet as puny as Pluto using the most powerful weapon known to man. Also, it’s worth keeping in mind that this is the bare minimum of energy that needs to be applied to Pluto to match its gravitational binding energy, so to destroy it, you’ll need a lot more bombs.

There’s also the question of how to distribute the weapons. Would you put them all in one place? Distribute them all around the globe? Perhaps burrow into the centre of the body? I suppose putting all the bombs in one place might be impressive, kicking a chunk of plutoid into space.

Now I must report these findings to @PlutoKiller himself, I fear he won’t be happy with the outcome of my calculations

Triton’s Ice Won’t Mix

Triton_sm

Triton, Neptune’s largest moon, hasn’t been studied in detail since Voyager 2 did a flyby in 1989. That was until a team headed by Will Grundy, a Lowell Observatory planetary scientist, did a 10-year study into the distribution of the moon’s ices.

Soon to be published in the journal Icarus, the team has found that concentrations of nitrogen and carbon monoxide mix together and form a covering of ice on the Neptune-facing side of Triton. This is in contrast to the methane content of the atmosphere. For some reason, methane is concentrated on the non-facing Neptune hemisphere of the moon. It appears that methane doesn’t like to mix with the other volatile ices.

This is in stark contrast to the non-volatile ices, such as water and carbon dioxide. Both appear to have a homogeneous distribution, regardless of phase or geographical location.

These are incredible observations of a moon that was once a Kuiper Belt Object. However, the infrared analysis carried out on Triton could be a test-run before observations are carried out on other, more exotic, targets.

This type of long-term, detailed analysis would be equally valuable for small icy planets like Pluto, Eris, and Makemake, all of which are similar to Triton in having volatile ices like methane and nitrogen on their surfaces,” said Grundy. “We have been monitoring Pluto’s spectrum in parallel with that of Triton, but Eris and Makemake are quite a bit fainter. It is hard to get time on large telescopes to monitor them year after year. We expect that Lowell Observatory’s Discovery Channel Telescope will play a valuable role in this type of research when it comes on line.”

Source: Space Disco, Discovery Channel (yeah, I’m referencing myself), Lowell Observatory

Moon Water, Confirmed

moon-water

The biggest factor hanging over human settlement of other worlds is the question of water. We need it to drink, we need it to cultivate food, we need it for fuel (indeed, we need it for the first lunar microbrewery); pretty much every human activity requires water. Supplies of water could be ferried from Earth to the Moon, but that would be prohibitively expensive and ultimately futile. For us to live on the Moon or further afield, H2O needs to already be there.

Ever since the Apollo lunar landings when samples of rock were transported to Earth we’ve been searching for the mere hint of this life-giving molecule. There have been indications that the lunar regolith may indeed contain trace amounts of the stuff, but on the whole, scientific endeavour has yet to return evidence of any large supply of water that could sustain a colony.

Until today.

Up until now, scientists haven’t been able to seriously entertain the thought of water on or near the surface of the Moon, apart from in the depths of the darkest impact craters. However, data from the recently deceased Indian Chandrayaan-1 mission has supported data taken by the Cassini probe (when it flew past the Moon in 1999 on its way to Saturn) and NASA’s Deep Impact probe (which made several infrared observations of the lunar surface during Earth-Moon flybys on its way to the 2010 rendezvous with Comet 103P/Hartley 2). Both Cassini and Deep Impact found the signature of water and hydroxyl, and now, a NASA instrument on board Chandrayaan-1 reinforces these earlier findings.

The NASA-built Moon Mineralogy Mapper (M3) on board the Indian satellite detected wavelengths of light reflected off the surface that indicated hydrogen and oxygen molecules. This is convincing evidence that water is either at, or near, the lunar surface. As with the previous measurements, the water signal gets stronger nearer the lunar poles.

So what does this mean for the future of manned space exploration? Although water has been detected, this doesn’t mean there are huge icy lakes for us to pitch a Moon base and pump out the water. In actuality, the signal indicates water, but there is less water than what is found in the sand of the Earth’s deserts (you can pack away the drinking straws now).

It’s still pretty damn dry, drier than anything we have here. But we’ve found this dynamic, ongoing process and the moon was supposedly dead,” University of Maryland senior research scientist Jessica Sunshine told Discovery News. “This is a real paradigm shift.”

If there are widespread water deposits (despite the low concentrations), even in regions constantly bathed in sunlight, there is huge potential for water deposits in those mysterious, frozen craters. Interestingly, these measurements indicate that the water may not have just been deposited there by comets; the interaction between the solar wind and the existing lunar mineralogy could be a mechanism by which lunar ice is constantly being formed.

Every place on the moon, at some point during the lunar day, though not necessarily at all times, has water and OH [hydroxyl],” Sunshine said.

We may see self-sufficient lunar colonies yet. But the saying “getting blood out of a stone” should probably be replaced with “getting water out of the lunar regolith”

Next up is NASA’s LCROSS mission that is scheduled to impact a crater in the south pole on October 9th. Analysis from the impact plume will supplement this positive Chandrayaan-1 result, hopefully revealing yet more water in this frozen region.

Sources: Discovery News, Space.com, Times.co.uk

xkcd: Probably Not The Best Way To Deal With An Asteroid

asteroid_xkcd

I hope we never see this day in the future, when the newscaster calmly informs us that an asteroid is on a collision course with Earth.

In any case, if this scenario did unfold, I’d like to think we’ll have the in-space technological capability to deal with the threat — but if we didn’t, I’m sure we’d work on it pretty damn quickly (given enough warning… if not… well, I’m out of ideas).

But please… don’t go strapping a nuclear warhead to the rock… it might not end quite so well.

Source: xkcd

Confirmed! Jupiter Was Hit By Something (Update)

Image captured by Anthony Wesley on 19th July 2009 at 1554UTC from Murrumbateman Australia.

Image captured by Anthony Wesley on 19th July 2009 at 1554UTC from Murrumbateman Australia.

On Sunday, SpaceWeather.com reported that an amateur astronomer from Australia had noticed a dark spot rotate into view on the Jovian surface:

The jet-black mark is near Jupiter’s south pole (south is up in the image). I have imagery of that same location from two nights earlier without the impact mark, so this is a very recent event. The material has already begun to spread out in a fan shape on one side, and should be rapidly pulled apart by the fast jetstream winds.” — Anthony Wesley

Although this was all very exciting, and conjured up memories from the Shoemaker-Levy 9 Jupiter impact in 1994 (as documented by Hubble), I think the majority of blogs and news websites were initially reluctant to proclaim that this new dark spot was the site of an impact by a comet or asteroid. Why? Well, these events aren’t supposed to happen very often. That’s why the Shoemaker-Levy 9 impact was termed “a once in a lifetime” event.

But, 15 years later (a dog’s lifetime, perhaps), it’s been confirmed by JPL (pending an official release) that the dark patch is in fact an impact site, and not some crazy weather system:

Glenn Orton from JPL has imaged this site using the NASA Infrared Telescope on Hawaii and confirms that it is an impact site and not a localised weather event.Update by Anthony Wesley

UPDATE (14:00 PST): Sky & Telescope Magazine is tracking developments, and reports that Leigh Fletcher, a scientist at the InfraRed Telescope Facility in Hawaii, is tweeting his findings from analysis of the Jupiter impact site. From the high infrared emissions in reflected sunlight off the dark spot, it is almost conclusive that the spot was caused by an impact by a comet or asteroid.

This has all the hallmarks of SL-9 in 1994 (15 years to the day!). High altitude particulates, looks nothing like weather phenom.” –@LeighFletcher

The most astounding thing for me is that this impact was initially observed by an amateur astronomer, and not a space agency. We await further word from Glenn Orton at JPL and Leigh Fletcher at Hawaii, but all indications suggest this black patch IS another impact crater…

A later image of the Jupiter impact (Anthony Wesley)

A later image of the Jupiter impact (Anthony Wesley)

More news to follow

Source: Anthony Wesley’s site