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Ion Rocket to Map Moon with X-Rays

CmdrTaco posted more than 9 years ago

Space 172

jralls writes "The Guardian is reporting that a European ion-rocket has taken the last year to reach the moon and is about to enter lunar orbit. Once it slows and gets into a very low orbit, it will probe the surface with x-rays in an effort to solve the long standing puzzle of the moon's origin."

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Visibile from Earth? (3, Interesting)

fembots (753724) | more than 9 years ago | (#10746952)

I wonder if we are able to observe this interplanetary tortoise from earth? If it passes the bright side in full moon, we should have quite a clear view of it since it's going so slowly.

Play iCLOD Virtual City Explorer [iclod.com] and win Half-Life 2

Re:Visibile from Earth? (1)

bsharitt (580506) | more than 9 years ago | (#10746992)

Why did it take so long to get to the moon?

Re:Visibile from Earth? (5, Informative)

NetKraft (785677) | more than 9 years ago | (#10747065)

Ion rockets can't generate very high accelerations. They can, however, keep going for a long time.

Re:Visibile from Earth? (1, Troll)

bsharitt (580506) | more than 9 years ago | (#10747092)

If we used some sort of higher powered rocket to generate the velocity, I wonder if ion rockets could hold that velocity for a long time.

Re:Visibile from Earth? (4, Insightful)

wertarbyte (811674) | more than 9 years ago | (#10747134)

If we used some sort of higher powered rocket to generate the velocity, I wonder if ion rockets could hold that velocity for a long time.

Since we are using this space, I wonder what we would need the ion rocket for to hold that velocity. In space, there is not much that could slow you down.

Re:Visibile from Earth? (1, Informative)

Anonymous Coward | more than 9 years ago | (#10747709)

>In space, there is not much that could slow you down.

True. Unless you are somewhat near a large gravity source that the rocket would have to fight against. The Earth for instance.

Re:Visibile from Earth? (1)

M1FCJ (586251) | more than 9 years ago | (#10747168)

I don't think there ever were any problems with holding the velocity. Acceleration, however...

Re:Visibile from Earth? (1)

Squarepusher (730147) | more than 9 years ago | (#10747365)

So the question is, if we used conventional rockets to quickly achieve a high speed, could the ion propulsion continue the excelleration after the rocket burns out?

Re:Visibile from Earth? (3, Interesting)

pe1rxq (141710) | more than 9 years ago | (#10747399)

That is exactly what this thing does...Use a conventional rocket to get away from earth's surface and then continue with ion propulsion to the moon.

Jeroen

Re:Visibile from Earth? (1)

bhima (46039) | more than 9 years ago | (#10747012)

I wonder if we'll be able to see the four elephants too.

Where do you think the Moon came from? (2, Funny)

mfh (56) | more than 9 years ago | (#10746953)

Place your bets!

I say the moon came from Uranus, what do you say? Here take a survey [opinionpower.com] !

Survey...

Uranus
Another Galaxy
Mars-sized planet crashed into the earth
Comet
Meteor
Microsoft
Another Dimension
It was a spaceship!
Cowboy Neal

Re:Where do you think the Moon came from? (5, Funny)

MrWim (760798) | more than 9 years ago | (#10746999)

It was a spaceship!
AKA "Thats no moon"

Re:Where do you think the Moon came from? (1)

mfh (56) | more than 9 years ago | (#10747014)

AKA "Thats no moon"

ROFTLMAO!!!!!

Re:Where do you think the Moon came from? (1)

A Boy and His Blob (772370) | more than 9 years ago | (#10747037)

I voted Microsoft, I imagine the EULA would go something like this:
By viewing or using light relected from the moon you agree to be bound by the terms of this License Agreement. IF YOU DO NOT AGREE TO THE TERMS OF THIS LICENSE AGREEMENT, LEAVE THE PLANET IMMEDIATELY AND/OR KILL YOURSELF.

Re:Where do you think the Moon came from? (1)

ForestGrump (644805) | more than 9 years ago | (#10747045)

Its actually Darth Vader in his death star orbiting above us..

I doubt the taxpayers would be willing... (0)

Anonymous Coward | more than 9 years ago | (#10747068)

...to fund x-raying Uranus. Even less for Cowboy Neal's Uranus.

Slashback (0)

Anonymous Coward | more than 9 years ago | (#10747480)

The Moon is a liberal myth!

Fist Sport! (-1, Troll)

Anonymous Coward | more than 9 years ago | (#10746958)

Yet another Euro-Space failure, like Beagle 2.

GET THE FUCK OUT OF OUR SPACE, LIMEYS!

Great title (4, Funny)

Chairboy (88841) | more than 9 years ago | (#10746966)

I expected the story to read "But when Flash Gordon approaches, will the moon people fight back with their electro-guns? Watch next week to find out!"

That was funny? (0)

Anonymous Coward | more than 9 years ago | (#10747827)

Maybe it was by some metric, but it sure as hell indicates a low acceptance threshold for comedy.

A year?! (0)

Anonymous Coward | more than 9 years ago | (#10746970)

WTF?

A trip to the moon took something like a few weeks in 60s and 70s!

Re:A year?! (5, Informative)

Garion Maki (791172) | more than 9 years ago | (#10747006)

unlike in the 60s and 70s, they are using ion engines for this mission, which can run of solar power.
they give less trust/second, but they can keep burning for allot longer, since the sun gives a constant supply of fuel (in the form of electricity from solar panels).
so you've got a smaller probe, which means easier to get into orbit from where it can fly on it's own power, so even tho it takes longer to get where you want, it will be cheaper to get it into orbit.

btw, they are planning on bigger engines in the future, so hopefully they will go faster someday.

Re:A year?! (5, Informative)

GileadGreene (539584) | more than 9 years ago | (#10747119)

Ion engines still use propellant (typically Xenon, but I haven't looked at what this particular mission is doing), they simply accelerate the propellant using electrostatic fields (in the case of ion engines) instead of chemical combustion. The key to ion engines isn't so much the solar power, as the fact that they have a much greater specific impulse (a rocket engineering term that relates to the efficiency with which propellant is used). Where a chemical engine may top out at ~400 s of specific impulse, ion engines have hit around 4000 s, or an order of magnitude greater propellant efficiency. That translates into a much smaller amount of propellant to do the same mission.

The tradeoff is betwen the extra time it takes to get to the destination (due to the low thrust of an ion engine), and the reduced cost created by being able to launch a much smaller amount of mass into space in order to do the mission.

btw, they are planning on bigger engines in the future, so hopefully they will go faster someday.

The issue with ion enginer thrust is not so much size, as it is power. The thrust you get is directly proportional to the amount of power you can generate. If you're using solar arrays, then you're limited to something between 15-20 kW (the Boeing 702 has solar arrays that produce ~15 kW at end-of-life).

Re:A year?! (0)

Anonymous Coward | more than 9 years ago | (#10747702)

Ion Engines aren't meant to be fast, they are meant to be able to continually be fired for long periods of time. Eventually, they will gain speed, but I doubt that using an Ion engine, we will gain much more speed instead of efficiency.

Re:A year?! (4, Informative)

Mr2cents (323101) | more than 9 years ago | (#10747810)

SMART-1 has been making bigger and bigger orbits around the earth, because of the smaller thrust explained above. It goes faster and faster, and because the craft gets further from the earth, it becomes easier to get into a bigger orbit. So at first the orbits became larger very slowly, but the last months it has grown faster than ever before.

The last months the orbit was also synchronized with the moon. The highest part of SMART-1's orbit coincided with the lowest point of the moon's orbit. This helps the craft to get an extra boost every month. Take a look at a graph of the orbit here [esa.int] .

Oh, and they do have normal propellant onboard, there's some 70kg left iirc. I think it was installed in case the ion engine failed, but I'm not sure of that. It could also be to correct the initial orbit if the launcher would have placed it in a wrong one. Anyway I *hope* it will be used to attempt a soft landing after the mission is over.

This begs the question: (0)

Anonymous Coward | more than 9 years ago | (#10746975)

Is Europe now going to take the lead in space exploration?

Re:This begs the question: (1)

mailtomomo (776971) | more than 9 years ago | (#10747096)

Not really : aluminium and silicium only ...

Re:This begs the question: (0)

Anonymous Coward | more than 9 years ago | (#10747107)

Yes, because the U.S. never launches space probes itself.

Re:This begs the question: (4, Insightful)

marsonist (629054) | more than 9 years ago | (#10747117)

... the beagle2 is laughing at your post all the way from mars

In all seriousness it's nice to see some other serious large-scale attempts being made by countries other than the US and Russia. As with all things scientific, the more head working together the more we all learn.

Re:This begs the question: (0)

Anonymous Coward | more than 9 years ago | (#10747364)

Prepare to laugh even louder, the parashute/airbag system used by Beagle 2 was built in the US ******

It's Destiny (-1, Troll)

Anonymous Coward | more than 9 years ago | (#10747560)

I agree with your comment, but it has to be acknowledged that history has proven again and again that it is the Destiny of the US to conquer space and be at the top.

Consider whose probes actually was successful in reaching Mars the most? US. Most of Russian attempts were failures. Even the recent Beage 2 proves the point.

Has anyone sent probes like Voyager and Cassini and such high profile missions with any levels of success? (Cassini was a success, but, Huygens (the ESA part) is yet to be seen.)

Also check out Bush. He made it very clear that it is his Destiny to be the President of the US of A. And he has been proven right again.

While everyone was being cowardly and foolish, he was the only one to be bold and wise enough to say:

If you are not with us, you
are with the terrorists.

...and rid the world of weapons of mass destruction and abominable terrorists.

NO (1)

mosb1000 (710161) | more than 9 years ago | (#10747622)

The first ion-powered spacecraft, Deep Space 1, was launched in 1998 by NASA. That's a lead of 5 years.

Re:NO (0)

Anonymous Coward | more than 9 years ago | (#10747739)

Soviet hall thrustors (similar technology) were first tested in space 1971. If anybody was first with this type of technology it was them.

Moon mining? (4, Interesting)

FiReaNGeL (312636) | more than 9 years ago | (#10746986)

From the article :

"The sun emits X-rays and these are reflected back into space by atoms on the Moon's surface. A magnesium atom will reflect an X-ray in a different way from an iron atom, and Grande's detector can detect these differences.

Flying over the lunar poles, so that it covers the entire Moon as it revolves below, Smart will create strip maps of the surface - and eventually a global map of its composition."

Look like useful data to me if we were in the 'mine the moon' business... maybe in a not so distant future?

Re:Moon mining? (1)

metlin (258108) | more than 9 years ago | (#10747121)

Cool!

Now that GWB is back in office, someone send up a note quick that there is oil and wealth on the moon!

Maybe something useful could come out of his re-election, afterall! ;)

Re:Moon mining? (1)

npross (564046) | more than 9 years ago | (#10747546)

That won't work! Tell GW that al Qaeda has a secret lunar base deep inside the moon and is using it as a terrorist training camp...

Re:Moon mining? (0)

Anonymous Coward | more than 9 years ago | (#10748163)

"Back in office" is misleading, because he didn't get kicked out of office. He would've been "back in office" if he had lost to Kerry and won in 2008.

Keep in mind.... (3, Insightful)

WindBourne (631190) | more than 9 years ago | (#10747208)

that it is not the whole moon. There are areas that light, and x-rays do not reach. Sadly, that is the most inteesting as it may contain ice.

Re:Keep in mind.... (3, Informative)

uberdave (526529) | more than 9 years ago | (#10747583)

That is not so. The sun shines (at one time or another) over the whole surface of the Moon, just like it shines over the whole surface of the Earth.

Re:Keep in mind.... (0)

Anonymous Coward | more than 9 years ago | (#10747633)

He's not talking about the surface.

MOD DOWN PARENT (4, Informative)

Anonymous Coward | more than 9 years ago | (#10747768)

At each pole, there are such deep caverans that sun never reaches it. That includes X-rays and normal sun light. That is why it is possible for ice to be there. And yes, it is considered part of the surface.

Re:Keep in mind.... (1)

MarkRose (820682) | more than 9 years ago | (#10748072)

There are some craters on the south pole of the moon which never get sunlight inside, which makes them a potentially good spot to collect volatile minerals. See more at Space.com's article on the south pole [space.com] .

META MODDERS, DO YOUR WORK (0)

Anonymous Coward | more than 9 years ago | (#10747878)

The info pointed here is absolutely factual. These mods are way off base. Go get them.

Re:Moon mining? (0)

Anonymous Coward | more than 9 years ago | (#10747315)

We're whalers on the moon, we carry a harpoon, but there ain't no whales so we tell tall tales and carry our harpoons.

A year to reach the moon? (2, Insightful)

ravenspear (756059) | more than 9 years ago | (#10746990)

I keep hearing that Ion propulsion is faster than what we currently use. What's with the incredibly slow travel time?

Re:A year to reach the moon? (5, Informative)

SpryGuy (206254) | more than 9 years ago | (#10747009)

The ultimate speed of ion propulsion is higher than that of chemical propulsion.

But the mass being expelled at high speeds (the ions) is so low, that accelleration is VERY slow. So it takes a long time to get up to speed, but the maximum speed you can theoretically reach is much greater than that of chemical rockets.

Re:A year to reach the moon? (0)

Anonymous Coward | more than 9 years ago | (#10747058)

Wouldn't it make sense then to have a booster attached the probe to get it up to speed, then switch to ion propulsion? You could even use inertia to carry you most of the way, while using the ion drive steering. In any case, what prevents them from attaching chemical boosters?

Re:A year to reach the moon? (0)

Anonymous Coward | more than 9 years ago | (#10747091)

You can attach boosters to anything. It just costs more.

Re:A year to reach the moon? (1)

someme2 (670523) | more than 9 years ago | (#10747578)

You can attach boosters to anything. It just costs more.
Bravo! Bravo! Encore!
From now on this line shall be known as my personal motto! It shall be enscribed in the family coat of arms. It shall be engraved in the family ring. It shall greet the trespasser when approaching the gates of the family manor.

A timeless truth to live by. Bold words to guide us.

Ah yes, and my new signature, too.

Re:A year to reach the moon? (4, Informative)

WindBourne (631190) | more than 9 years ago | (#10747244)

There was no extra weight margins on the launch vehicle to do so. However, if you have a more powerful booster (i.e. lots more money), you can then get higher intial speed.

This mission was to prove to EU that their ion engine worked. So they wanted it to keep running for quit some time. NASA did this be creating deep space one, which ran around picking up steam via its ion engine.

Down the road, you can bet that EU will launch a number of deep space probes based on ion engines with high initial speeds.

In addition, their will be a real push for micro sats with ion engines to control them. Makes a lot of sense to send these to other planets. think of 100 small satillites going though out jupitor or saturn planets. Or better yet, small micro sats around Mars providing surface to space communication, pictures, glp, etc. Send about 100 of these to orbit mars and we would have a very through pic of mars, moon, etc.

Re:A year to reach the moon? (2, Interesting)

bpd1069 (57573) | more than 9 years ago | (#10747298)

I bet when this technology becomes the norm for deep space probes they will use the gravitational sling shot effects rather than attach boosters. Its going to take a while for any deep space probe to get to its destination, so why not use free (as in mass) to help you get there?

I wonder how much of a boost the Sun can give you? (ala Star Trek)

Re:A year to reach the moon? (4, Informative)

GileadGreene (539584) | more than 9 years ago | (#10747131)

Actually, the maximum speed that you could theoretically reach is the same in both cases: c

The difference is that it will take a chemical rocket much more propellant to get there, because it is far less efficient in its use of propellant mass (i.e. it has a lower specific impulse).

Re:A year to reach the moon? (1)

216pi (461752) | more than 9 years ago | (#10747930)

I thought nithing with a mass could be accelerated to c since it would take an infinite ammount of energy to accelerate it to c since the mass of the object grows the more it reaches c.

Re:A year to reach the moon? (1)

marco0009 (716718) | more than 9 years ago | (#10748070)

You are correct, as an object approaches the speed of light, the object's mass increases, requiring exponential quantities of fuel as the object approaches c.

Re:A year to reach the moon? (2, Funny)

plj (673710) | more than 9 years ago | (#10747182)

I think they should have used Twin Ion Engines [wikipedia.org] to get a little better acceleration...

Re:A year to reach the moon? (5, Informative)

Brett Buck (811747) | more than 9 years ago | (#10747897)

> The ultimate speed of ion propulsion is higher than that of
> chemical propulsion.

Depending of course on the fixed mass of the spacecraft, vs it's propellant mass, of course. You get more momentum change from given amount of propellant, but if you only had a teaspoon full of propellant, or the spacecraft was exceptionally massive, you wouldn't get more velocity.

> But the mass being expelled at high speeds (the ions) is so
> low, that accelleration is VERY slow. So it takes a long
> time to get up to speed, but the maximum speed you can
> theoretically reach is much greater than that of chemical
> rockets.

To expand, the measure of efficiency of a rocket engine is the specific impulse or ISP. It's how much momentum change you get per unit of propellant mass, and the usual unit is seconds (lb-sec/lb). The highest actually-achievable ISP from a chemical rocket is somewhere in the 475 seconds. The Saturn 5 first stage was more like about 350, and monopropellant thrusters used for many satellite propulsion systems is more like 150-180! That means that if you want to change the velocity a lot, you need a whole lot of propellant.

I'm not sure which engine this particular program uses, but the ISP of the typical Xenon ion thruster is something like 1800. So you have to carry fantastically less propellant for a given velocity change, meaning it can weight less at liftoff, meaning you can use a weaker/cheaper booster.

The downside is that you don't get something for nothing. It takes, not surprisingly, a whole lot of electrical power to make it go. So you put in 4000-5000 watts of power, and it only generates .04 lb of thrust - .64 of an ounce, pushing a spacecraft weighing thousands of pounds on the ground. So the acceleration is very small, meaning takes a long time to get going. The other downside is that the Xenon ions, although chemically pretty neutral, shoot out at such high speeds that anything that gets in the exhaust gets eaten away. This may or may not be an issue depending on there you put it relative to the rest of the spacecraft.

Brett

Re:A year to reach the moon? (3, Funny)

Anonymous Coward | more than 9 years ago | (#10747016)

They are using euro ions, which require extended committee meetings and discussions before determining the appropriate direction in which to apply their force.

Re:A year to reach the moon? (0)

Anonymous Coward | more than 9 years ago | (#10747028)

Have you read the article? Oh, sorry, I forgot your the same kind of moron that usually doesn't rtfa.

Re:A year to reach the moon? (0)

Anonymous Coward | more than 9 years ago | (#10747035)

It's not faster per se, it's simply a much more efficient engine. Although the thrust is actually pitifully small compared to a rocket (thereby having VERY slow acceleration), over a long distance in the vacuum of space it will be able to attain greater speeds and distances via far better fuel conservation than a rocket. The rocket is a sprinter while the ion drive is a marathon runner.

At least that's my understanding of the situation.

Re:A year to reach the moon? (1)

InternationalCow (681980) | more than 9 years ago | (#10747061)

What you heard is that the specific impulse is way larger than with chemical, meaning that the exhaust velocity is very high. That means that you have a very efficient means of propulsion, with each particle of exhaust producing more thrust/particle than chemical rockets do. The exhaust being a tenuous gas however, the actual THRUST is very low (and the thrust/weight ratio even more so). Because it works in the vacuum of space and can run for years on end, the eventual velocity that this low thrust can impart on the craft is pretty impressive.

Re:A year to reach the moon? (1)

Lawrence_Bird (67278) | more than 9 years ago | (#10747385)

shouldnt this have had a fairly substantial speed to start? Ie, the space torch orbits about 29,000 Km/hr which is about the minimum for low earth orbit.

This is insane! (2, Funny)

Anonymous Coward | more than 9 years ago | (#10747007)

Anyone still using film up there is going to be pissed when their exposures are ruined.

It's from Wisconsin. (3, Funny)

bs_02_06_02 (670476) | more than 9 years ago | (#10747017)

Everyone learns that the moon is made of cheese in the cartoons. I bet they'll say it's from Wisconsin.

New tourist slogan (3, Funny)

macrom (537566) | more than 9 years ago | (#10747052)

"Come to the moon and smell our dairy air!"

Doesn't quite have the same ring...

Re:It's from Wisconsin. (0)

Anonymous Coward | more than 9 years ago | (#10747602)

But if you learned it from claymation instead, you'd know that that the Moon is pure Wensleydale cheese.

Choose your cheeze (2, Funny)

Nomeko (784750) | more than 9 years ago | (#10747018)

Finally we can have proofs that the moon is made out of cheese..

I do hope it's cheddar..

Don't be Silly (0)

Anonymous Coward | more than 9 years ago | (#10747258)

Everyone knows it's made of Pepper Jack.

Unfortunately... (0, Troll)

jmcmunn (307798) | more than 9 years ago | (#10747022)


Unfortunately, when this rocket left earth a decade ago, digital photography wasn't around so they were forced to use 35mm film onboard to map the surface. This means we will have to wait for the rocket to make its 20 year return to earth before seeing any results.

(yes I know they don't use 35mm film or your typical kodak digital camera on these space vehicles, so don't bother telling me)

MOD parent down (0)

Anonymous Coward | more than 9 years ago | (#10747167)

uh... since when is Sept. 2003 a decade ago?

also....we had probes in the 60s that didn't have to "return" to earth to send back pictures

Re:Unfortunately... (-1, Redundant)

Anonymous Coward | more than 9 years ago | (#10747170)

Troll? I think this was likely a joke, someone mod this underrated or funny or something at least. Jeez, the weekend Slashdot crowd have got a collective stick up their ass.

Possible Resolution to US moon landing hoax theory (5, Funny)

jeoin (668566) | more than 9 years ago | (#10747034)

Will these guys be able to snag some good shots of the trash we left on the moon? Exluding the flag of course, which can't be trash cuz its on a stick.

Re:Possible Resolution to US moon landing hoax the (1)

Garion Maki (791172) | more than 9 years ago | (#10747071)

if you know what the trash looks like on x-ray, then you could try searching for it... I think they are more interested in the rocks below the trash tho, so the camera's are probably designed to see that and not the surface (with the trash).

British-made detectors? (-1, Troll)

Gordonjcp (186804) | more than 9 years ago | (#10747060)

Does that mean that once it gets into lunar orbit it will piss oil then flatten its batteries despite nothing being left switched on?

Re:British-made detectors? (OT!) (1)

TWX (665546) | more than 9 years ago | (#10747282)

You know why the British don't build computers, right?

They haven't figured out how to make them leak oil yet...

Which reminds me.... (0, Offtopic)

Enoch Zembecowicz (698998) | more than 9 years ago | (#10748131)

Q: Why do the British drink warm beer? A: Because Lucas makes their refrigerators.

A Space Odyssey (2, Funny)

Toutatis (652446) | more than 9 years ago | (#10747062)

Isn't that the way the monolith will be found?

Re:A Space Odyssey (1)

StuckInSyrup (745480) | more than 9 years ago | (#10747311)

That's 3 years too late. Our civilisation is doomed.

wow (4, Funny)

flacco (324089) | more than 9 years ago | (#10747077)

sobering thought that that headline sounds exactly like something you might hear in a pulp sci-fi movie from the 50's...

Re: wow (2, Funny)

Black Parrot (19622) | more than 9 years ago | (#10747156)


> sobering thought that that headline sounds exactly like something you might hear in a pulp sci-fi movie from the 50's...

Science has finally caught up with fiction!

S.M.A.R.T 1 (1)

DeathByDuke (823199) | more than 9 years ago | (#10747173)

I'm hoping this Ion drive driven S.M.A.R.T 1 will do interesting things like find those elusive water deposits, map the small unchartered areas of the far side (I bet theres still some) and even try and locate the Apollo landers.

The last one will be the coolest for obvious reasons, the first one would be the most profound, for the proposed colony, and the second one, a fuller, completer map of the moon for the future explorers on the surface. It wouldn't surprise me though if a GPS system was set up by then anyway.

Back on subject, this should showcase the usefulness of Ion drives, and prove their application as a propulsion method for little 'inner system' trips like this. (Ion drives were already proven with Deep Space 1 for inter-system propulsion) I doubt they will get used for human ships though, too slow.

From the article -- galactic bowling physics? (4, Insightful)

jdkane (588293) | more than 9 years ago | (#10747179)

Smart's map should provide that data and show if scientists are right in believing that the Moon coalesced from a vast ring of debris generated when an ancient planet the size of Mars destroyed itself after crashing into Earth. Understanding the origins of the Moon will therefore give insights into the nature of our planet.

Doesn't this mean earth should have some huge dent in it, and not be so round? Look at the sizes of Mars and Earth [nasa.gov] . Are you surprised earth is still here after a crash of that magnitude? I am. Maybe earth was a lot bigger before a Mars-like planet destroyed itself crashing into earth, but then I go back to my question about the roundness of the earth.

Maybe someone more knowledgeable wants to talk about that. The article doesn't go into any great detail on that, which causes a lot of questions to be raised.

Re:From the article -- galactic bowling physics? (1, Informative)

Anonymous Coward | more than 9 years ago | (#10747206)

The eart wasn't a solid mass 4 billion years ago. It was molten.

Re:From the article -- galactic bowling physics? (3, Informative)

jdkane (588293) | more than 9 years ago | (#10747271)

Thanks. Your information enabled me to do some googling.

For anybody who is interested, here's a theory [uc.edu] (bottom of the page): "one theory says the moon formed when a big, molten chunk of crust was knocked/blown off from the rest of the planet". And much more info [google.ca] about it.

Re:From the article -- galactic bowling physics? (4, Informative)

The Mgt (221650) | more than 9 years ago | (#10747403)

The earth wasn't a solid mass 4 billion years ago.

It's still not a solid mass now.

Re:From the article -- galactic bowling physics? (1, Interesting)

Anonymous Coward | more than 9 years ago | (#10747229)

Any planet (or asteroid, or whatever) above a certain mass will become spherical under its own gravity. I don't have the numbers at hand, but it is surprisingly low, if I recall correctly it would have to be roughly 30 miles wide to have enough mass.

Re:From the article -- galactic bowling physics? (1)

gnatman64 (688246) | more than 9 years ago | (#10747241)

I saw something on the Science Channel about this, and the illustration they had involved the two planets hitting each other and swirling around a bit. Since the earth is mostly moltent rock, I think during the collision, a lot of that came in to fill it in. Plus this was a long long time ago, so the Earth could have covered it up by now. Not the best explaination I know, I can't say I understand it all myself.

Re:From the article -- galactic bowling physics? (1)

DarkKnightRadick (268025) | more than 9 years ago | (#10747283)

Don't forget that the Earth was molten at the time, and even if it wasn't, look at what is left of the Yuccatan crater due to the forces of erosion. Wind and water are very, very powerful forces.

Re:From the article -- galactic bowling physics? (3, Informative)

Anonymous Coward | more than 9 years ago | (#10747284)

There was once a theory that the Pacific Ocean was the hole left when the moon was pulled out of the Earth, but...

There is a reason why small objects, like asteroids, are often irregular in shape, while large objects, like planets, tend to be nearly spherical. All parts of an object are attracted to each other by gravity, this tends to pull the object into a spherical shape. Above a certain size (which depends on the materials involved) the object is not strong enough to maintain its shape and collapses into a sphere. Also, even now, the Earth is mostly liquid or softened by the heat, and the collision would have released so much energy that it probably re-melted any part of the Earth that had solidified by then. Add to that the effects of billiions of years of plate tectonics and you would not expect to see the hole.

Biq == Round (4, Insightful)

DumbSwede (521261) | more than 9 years ago | (#10747404)

Beyond a certain size, gravity pulls things into a spherical shape. The immense pressure makes the insides molten and irregular structures eventually sink down in. Mars has Mons Olympus, the tallest volcano in the solar system, this is because Mars is smaller and has less gravity than Earth. The larger the planet the more regular it has to be. Asteroids can be highly irregular because they haven't the size and gravity to collapse them into spheres.

The mountains on Earth may appear huge to us insects on the surface, but from a distance the earth appears as smooth as a billiard ball.

Ironically this event was so big, that unlike latter smaller hits, all evidence in the way of dents will be gone as the entire globe virtually liquefied and coalesced again. Though I wouldn't rule out some exotic mass distributions that might lend evidence of it.

Re:From the article -- galactic bowling physics? (0)

Anonymous Coward | more than 9 years ago | (#10747553)

Essentially the Earth broke apart too. There was a show awhile back that had a simulation of a mars like planet hitting the Earth, and it wasn't pretty. It looked like a bead of water being hit at high speeds by another bead of water. Then the planets reformed into spheres, one just bigger than the other. This of course, was a long time ago.

Re:From the article -- galactic bowling physics? (4, Interesting)

barakn (641218) | more than 9 years ago | (#10747935)

Take a look at the moon. Those dark spots are the sites of enormous ancient impacts. They may have been holes briefly, but they then filled up with lakes of lava. As far as the Earth goes, the impact was so devastating that the outer layers of the Earth had to reform by falling back down.

The following contains some links to mostly non-technical explanations of planetary roundness. I'd like to point out that part of this explanation [sciam.com] , by "Derek Sears, professor of cosmochemistry at the University of Arkansas and editor of the journal Meteoritics and Planetary Science," is wrong. He says "Planets are round because their gravitational field acts as though it originates from the center of the body and pulls everything toward it." But this is a circular argument (pardon the pun). Generally a non-spherically symmetric distribution of matter doesn't have a gravitational field that acts as if it originates from the center of the body (the "center" being the center of mass). Spherically symmetric mass distributions do have this special property, so what Sears really implied is that planets that are already round will have gravitational fields that point towards the object's center of mass. This does absolutely nothing to address cases of objects that deviate from perfect roundness, i.e. all celestial bodies. This explanation [astronomycafe.net] by Dr. Sten Odenwald suffers from the same argument, and there's even a hint of it here [nasa.gov] . Nonetheless, these explanations are approximately true, and require bizarre shapes to break them.

For example, imagine a homogenous, perfectly shaped doughnut (a torus with a circular cross section). At the center of the doughnut hole we'd feel no gravitational field at all (a perfectly balanced tug-of-war). But deviate from the exact center just a tiny amount, and the closer side of the doughnut becomes more attractive than the other. One suddenly experiences a gravitational field that points away from the center of mass.

It's George Bush's Moon Mandate. (2, Funny)

eBayDoug (764290) | more than 9 years ago | (#10747202)

Free X-rays for all Moon residents. Take that Canada!

Re:It's George Bush's Moon Mandate. (1, Informative)

Anonymous Coward | more than 9 years ago | (#10747775)

This is an EUROPEAN spacecraft.

Just remember... (2, Funny)

boola-boola (586978) | more than 9 years ago | (#10747306)

....what happened when they probed Mars with X-rays! Watchout! (is Gary Sinise piloting?)

It's about damn time.... (0)

Anonymous Coward | more than 9 years ago | (#10747319)

Figures, people are going to talk about going to Mars and how long it's going to take to get there etc, and here we have a perfectly good place to practice, the moon, it's been there, forever, and we still don't know jack about it. Does not give me much faith in the space program to think that we are talking about space stations and other galaxies when we don't know what we're doing with the rock right next to us, and it's not NASA, it's Europe! The US space program really needs to shape up.

- Saturn SL1-WNY - Propz: GNAA

Opposed by GNAW&NPS (1)

AndroidCat (229562) | more than 9 years ago | (#10747349)

Scientists believe nuclear-powered ion-drives are their only real hope of exploring deep space, and vigorously support their development. Not surprisingly, anti-nuclear protesters, like the Global Network Against Weapons and Nuclear Power in Space, have pledged opposition.
Too much time on Slashdot. Any group that starts GNA... automaticly activates my mental filters. (No great loss in the case of Huggers In Space.)

-- Ion Rocket to Map Moon with X-Rays (0)

Anonymous Coward | more than 9 years ago | (#10747522)

We just _have_ to make sure there's no life there, right?

Scientists Discover Moon Core Made of Cheese (0, Redundant)

TheSpoom (715771) | more than 9 years ago | (#10747737)

News at eleven.

from 'dept' topic (2, Interesting)

deunan_k (637851) | more than 9 years ago | (#10748141)

Posted by CmdrTaco on 01:06 AM -- Monday November 08 2004
from the dept.


I've always read the 'from the so and so and whatever dept' cuz it's humourously funny and cynic at the same time.

This time, it's just plain ol' from the dept. I just wonder, whether it is an oversight or CmdrTaco really does not have anything witty to say about it? :-P

I know, I know it is off-topic, mod me down then.. I probably deserve it.


The ion drive is the real story (5, Interesting)

SimURL (822939) | more than 9 years ago | (#10748317)

Ion drive technology allows you to explore space in ways that chemical rockets simply can't.

Quoting from the article,
"We have shown that even a small ion engine like Smart's can get us across space. Now we are planning to build space telescopes and robot probes to planets such as Mercury, using bigger and more powerful ion engines. These will take years off space-travel times. Instead of decades-long missions, we will take only a couple of years to cross space for future projects."

But,
"Ion engines need electricity and only solar panels can provide enough at present. So ion engine missions will be restricted to planets and moons near the Sun."

So the solution to deep space exploration is nuclear-powered ion-drives and NASA is working on it.
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