Robotic exploration for the planets; Humans for the Moon
Radiation prohibits human journeys of any length outside the Van Allen belts. Shielding is just too heavy for our technology today.
Robots for the planets; Humans for the Moon.
Boffins have discovered that Mercury - closest planet in our solar system to the Sun - has had a magnetic field for nearly four beeellion years. As The Register previously reported, NASA's Messenger spacecraft slammed into the alien world – which is Sol's closest neighbour – late last month. Before its crash landing on the …
"Radiation prohibits human journeys of any length outside the Van Allen belts. Shielding is just too heavy for our technology today."
The shielding is not beyond our technology at all. Getting a sufficient mass of aluminum, water, liquid hydrogen, food, poop, and/or other proposed shielding materials into space is not a technological problem, but a logistical question of "How many launches do you want to perform to complete your shielded ship?" The resulting answer is split between launches for shielding and launches for the extra propellant needed to push the shielded ship around.
The Apollo capsules were quiet well shielded considering how lightly they were built. The August 1972 solar storm would've been fatal to astronauts on the moon or in the LEM, but anyone in the capsule would've "only" taken 35 rem from the experience.
How can you tell a magnetic field is 4 Billion Years old?
If you're measuring the field it's like using a compass, so the magnetic field is now
As the craft hit the planet, how could they read age of the field?
It's not like they have a load of magnetic samples to compare
How can you tell a magnetic field is 4 Billion Years old?
Certain types of rock retain an imprint of the magnetic field of the time they were formed. That imprint itself effects the magnetic field of the planet, but the affect is highly localised. If you get sufficiently up close and personal you can begin to separate those imprints on the surface rocks from the greater bulk of the planetary field, estimate the age of the rocks and you can then determine what the planetary field as a whole was at that time.
At least that is what they are claiming, I haven't delved deeper than the abstract and it isn't my specialism. Personally I find it surprising that sort of unraveling of a messy dataset can be done at a range of tens of kilometres, but I certainly haven't the background to contradict them.
Unfortunately we're still going to have to burn you at the stake for getting 'affect' and 'effect' the wrong way round.
I actually noticed that one was wrong with two minutes of the edit window still open, so quickly edited and changed affect to effect. Noticed a couple of minutes later that I'd actually changed the wrong one but by that time the edit window was shut. ;-)
mad physicist Fiona
"Personally I find it surprising that sort of unraveling of a messy dataset can be done at a range of tens of kilometres, but I certainly haven't the background to contradict them."
That was my point, geologists can determine magnetic field shifts, by looking at rocks. Did they have some expendable geologists on the craft that jumped out, drilled a core sample and measured the magnetic field reversals? I bet they were a happy bunch for about 1 second or until they vaporised.
Thats why i don't get it. I think you need actual rock samples to measure. Or am I completely wrong?
My Geologist friends are now complaining!
You can measure magnetic variation non-invasively. In archaeology we use handheld magnetic gradiometers which we cart around fields a few cm above the ground, and measure in the tenths of a nano Tesla. I know that people take magnetometers up in aeroplanes to measure the strength of the geological magnetic field when prospecting for oil, but they measure at many orders of magnitude coarser then archaeologists.
And yes, it is possible to compare the current magnetic field with that which is "locked" into rock when it cooled, and run that through models to give an appropriate age. I must admit though, 10s of km altitude is quite impressive for these sort of techniques. Although archaeologists often use equipment older than the stuff they're looking for...
Of course they didn't it for a single rock. But if a large enough area formed in the same time, say from melted rocks, it may have retained the old field, and today 'disturb' the actual field and that disturb being detectable flying low enough so the instruments read just a small enough area of the planet field.
It is also true for local gravimetric changes. If you fly high enough big mountains (or even local changes in density) don't matter much, but if you fly close enough to them you can measure a difference in the gravity force.
The Reg text is very misleading when it says "boffins have learned it if 4bn years old"
What was said is:
" We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years."
What that means is they gathered some data and stuffed it through some mathematical models they have and got the numbers.
Like all mathematical models, these are based on assumptions about how processes work and that it is valid to, say, use a model derived on one planet with data coming from another planet.
They really haven't learned anything.
They really haven't learned anything.
That's a misstatement in an absolute sense, and an epistemological category error.
The absolute (epistemologically neutral) error: The scientists reporting this have learned a number of things, assuming they're neither deluded nor mendacious. They've learned what data was reported by the craft, and what results their models reported, for example.
The category error is the persistent belief among some that scientific epistemology endorses some foundational difference between modelling and similar computational exercises (considered non-privileged by adherents to this peculiar religion) on the one hand, and some other set of elucidary procedures on the other - typically empirical measurement and/or formal derivation. In fact privileging the latter at the cost of the former is precisely opposed to modern scientific epistemology, since it is in itself a subjective evaluation; and it's a failure of critical thinking, since it refuses to recognize that the only scientific bridge from empirical measurement and formal manipulation to supporting or contesting1 a hypothesis is through a model, because meaning does not inhere in the objective world. Models can be computable or not2, but they're indispensable.
1Some, following the sort of theory of scientific epistemology advanced by Popper and that ilk, would have "confirming or refuting" here. But a perfect Baysian reasoner recognizes that the probability of a hypothesis' correctness is in the open interval (0,1) - it only approaches complete confirmation or refutation asymptotically. The best you can do is support or contest to within some epsilon of certainty.
2Though non-computable models are not often terribly useful in the hard sciences.
...from the clever chaps who build these things.
They regularly seem to be able to make these probes last far longer than envisaged. That's real value for money, especially when everywhere we send one of these things turns out to be far more interesting than anyone ever envisaged.
Example: Places in the solar system that do or might support life: when I was born, 1 (earth), today 3+ (Europa, Encheladus, maybe Ganymede...)
They regularly seem to be able to make these probes last far longer than envisaged.
Ah yes, they just engage the Scotty Principle.
To quote Star Trek III:
James T. Kirk: How much refit time before we can take her out again?
Montgomery Scott: Eight weeks, sir -- [Kirk opens his mouth] -- but ye don't have eight weeks, so I'll do it for ye in two.
James T. Kirk: Mr. Scott. Have you always multiplied your repair estimates by a factor of four?
Montgomery Scott: Certainly, sir. How else can I keep my reputation as a miracle worker?
James T. Kirk: [over the intercom] Your reputation is secure, Scotty.
"They regularly seem to be able to make these probes last far longer than envisaged. That's real value for money, especially when everywhere we send one of these things turns out to be far more interesting than anyone ever envisaged."
What happens is that they design to a certain specification, e.g. all systems fully functional for 18 months. That helps with budget planning because someone has to stay in contact with the craft for that length of time to ensure everything is working and that the observation data are coming back OK. Basically, it's like saying, "if we spend $100 million dollars on this probe, how long do we think would be a good length of time for it to be operational?" This 'time budget' also helps when engineering the probe to work out what sort of tolerances are required for the components or the necessary amount of propellant for the planned mission length. It's not all that much different from designing a car. The manufacturer plans its useful life to be about 5 years, but it will generally keep going far longer than that.
"As The Register previously reported, NASA's Messenger spacecraft slammed into the alien world – which is Sol's closest neighbour – late last month."
I thought Venus was our closest, or is the article alluding to a specific point in time when this construction could be deduced?
It's ok talking about 'magnetic fields locked into rocks' but has anyone managed to check out the surface of Mercury recently? As I recall it's got more cratering then a McD loving teenager's frontage ... Surely the extensive reformation of the surface affects the local magnetic field very strongly and the impactors themselves generate huge magnetic anomalies?
I don't understand ...
Even if you are a devout Christian, nothing says you have to believe everything, especially the old testament. "Creationism" is part of a Fundementalist Dogma that few believe in anymore. When you get to literal interpretations of dead languages you are bound to be way off. Dates and age in particular as the concept of billions of years was as foreign as space flight.
"Those tiny signals revealed that Mercury’s magnetic field is very ancient, at least 3.7 billion to 3.9 billion years old. The planet itself formed around the same time as Earth, just over 4.5 billion years ago."
Just suppose life started on Mercury when the Sun was not a pure melter, and as time went on it heated up, and the Mercurians thought, "Cop this for a game of soldiers, let go somewhere cooler!"
And there just happened to be this handy little planet nearby, with just the right environment and occupied by large meat based occupants (handy food supply).
And the rest, as they say, is history
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