[dissident]

I am all for it, 40% gravity should do wonders for aching joints and especially back problems.

I wouldn't be so sure. Your skeleton and muscles would atrophy and it is not clear that the amount of atrophy would be benign.

Anyway, 40% of back problems are from bacterial infection of the spinal disks by the species of bacteria that occurs in acne (they enter through your gums). Aching joints are likely rheumatoid arthritis, which is an auto immune disease. In neither case will you get any relief from lower gravity.

I have spinal osteoarthritis, in theory lower gravity would cause less compression on my damaged structure.

It would be only transient relief. Eventually the benefits would disappear as a new equilibrium is established. There ain't no free lunch.

[dissident]

So, with bones deteriorating in zero G, given only a few generations of reproducing, humans could become gelatenous, like jellyfish.

Sorry. That thought fascinates me. No bones about it.

We do not know enough to even say if we could propagate as a species. The bone loss is not a genetic adaptation but a pathology. Humans have never adapted to this pathology so in all likelihood it will have negative effects on health.

[Tanada]

I am all for it, 40% gravity should do wonders for aching joints and especially back problems.

I wouldn't be so sure. Your skeleton and muscles would atrophy and it is not clear that the amount of atrophy would be benign.

Anyway, 40% of back problems are from bacterial infection of the spinal disks by the species of bacteria that occurs in acne (they enter through your gums). Aching joints are likely rheumatoid arthritis, which is an auto immune disease. In neither case will you get any relief from lower gravity.

I have spinal osteoarthritis, in theory lower gravity would cause less compression on my damaged structure.

It would be only transient relief. Eventually the benefits would disappear as a new equilibrium is established. There ain't no free lunch.

Honestly it is a fond daydream, I have had to stop taking my arthritis medication because it was causing ulcers so now I get chronic pain and limited mobility unless I choose to have constant cramping and bleeding ulcers as the alternative. Hopefully they will come up with a new medication soon.

[ChilPhil1986]

To be honest, I can't justify the energy expenditures of space flight unless it's for the purpose of launching data-gathering satellites or, by some serious string of miracles we figure out how to terraform another planet to suit a colony.

I grew up with Apollo 13 as my favorite movie and I used to believe colonization of space was destined to happen, but my discovery of peak oil put NASA's achievements of the 1960's through to the present day in perspective.

A space colony is optimistically 100< years away in engineering terms with presumed unlimited energy resources. Since I believe western society will reach a decline within the next decade due to symptoms of peak economic oil production, I'm firmly in the 'What's the friggin' point?' boat with regard to space exploration.

On that topic of colonization, anyone outside of Earth's magnetosphere longer than a couple months dies of cancer from high-energy radiation from the Sun, and last I checked, Mars does not have one. The physics behind how the Earth even generates this phenomena isn't understood all that well either, and unless we want everything we bring to Mars encased in lead, I would suggest we figure out how the Earth does what it does so that we can emulate it on a smaller scale to suit our needs.

As expressed earlier, I highly doubt we have that kind of time. These pointless private venture manned flirtations with space are borderline unethical, and should be ceased immediately. The existence of the ISS is still somewhat justifiable since its purpose at this point is mostly scientific, although my hopes for what game-changing knowledge could be gleaned before the party comes to a halt get more grim by the year.

Knock it off, Bransen. If he wants to bankroll further space exploration, I'm sure NASA would love some wealthy donor backing. I'm not sure what (if any) red tape blocks that, but that would be the best way for his millions to get spent.

[dissident]

The magnetic field acts to duct the solar electrons and protons into the geomagnetic polar caps, but it is the atmosphere itself that is the main shield. Only galactic cosmic rays, which are ultra high energy protons and nucleons, can penetrate down to the surface. They actually do not reach the surface directly and it is particle collision products that propagate the energy (just like in particle accelerators). The peak energy deposition is between 12 and 13 km above the surface. So the atmosphere is doing a very good job protecting us.

On Mars the surface pressure is 0.7 hPa, which on Earth corresponds to between 50 and 60 km above the surface. With such a thin atmosphere all of the GCR would hit the surface and a very large part of the energetic part of the solar wind. Coronal mass ejection events and the associate proton flux would also reach the surface. On Earth, they taper out by 20-30 km above the surface. The 1989 CME event managed to have a significant fraction of the proton flux reach 10 km above the surface and brought down the Quebec electrical power grid.

Most of the scifi portrayal of Mars has it as some sort of Earth-like planet that can be made livable and many people have this impression. It is nothing of the sort, it is a glorified moon and any colony would have to live in radiation shielded compounds that maintain a breathable atmosphere with sufficient pressure and the right composition. Just like any base on the Moon. Space is no escape and we have to make sure we do not trash the only livable planet within our reach.

[ChilPhil1986]

Interesting, dissident. If such is true, then there's really no chance of Mars colonization due to Mars' smaller mass being incapable of holding a sufficiently thick atmosphere.

Now I am curious to know if the ISS was up and floating during the 1989 CME. If so, I wonder how they felt the effects since they are outside of the 10km bubble you described.

[dissident]

Interesting, dissident. If such is true, then there's really no chance of Mars colonization due to Mars' smaller mass being incapable of holding a sufficiently thick atmosphere.

Now I am curious to know if the ISS was up and floating during the 1989 CME. If so, I wonder how they felt the effects since they are outside of the 10km bubble you described.

I did not say that the geomagnetic field has no impact, but if it were turned off tomorrow the ionizing particle precipitation would not be bathing us at the surface. Right now the electrons and protons from the solar wind are being ducted towards the geomagnetic poles but it is rather clear that surface radiation at these latitudes is a non issue. GCR, due to its high energy, is not trapped by the magnetic field to the same extent as most solar wind electrons and protons and only has a weak maximum in the geomagnetic polar caps with a large amount of flux in middle and low latitudes.

There are experimentally verified range-energy relations for electrons and protons in air and other substances like metals. High energy electrons will easily penetrate 1/4 inch aluminum hulls used on spacecraft. The ISS is in LEO and misses most of the solar wind flux since it is trapped by the geomagnetic field. Shuttle astronauts reported getting sparkles in their eyes when they were in an orbit 1000 km above the surface instead of the usual 380 km. They left the relatively quite zone of the Van Allen belts.

http://en.wikipedia.org/wiki/Halloween_ ... orms,_2003

The ISS crew had to stay in the shielded portion during the October 2003 CME event. Protons are more easily stopped by metal compared to electrons.

[Withnail]

Now I am curious to know if the ISS was up and floating during the 1989 CME. If so, I wonder how they felt the effects since they are outside of the 10km bubble you described.

The ISS hadn't even been thought of in 1989.

[MD]

Homo Sapiens will not do this job. If ever built, it will be by self-aware and self-replicating machinery along with genetically created beings well-suited to the conditions.

Homo Sapiens might come visit, if they are around long enough.

Slim odds, at best, from where we sit today.

Very slim.

[Sixstrings]

The ISS hadn't even been thought of in 1989.

It was "thought of" even back in 1987. At first it was supposed to be an American space station, then all the budget cutbacks started and they looked to international cooperation.

Actually it was first approved by Ronald Reagan and he announced it in his 1984 state of the union speech.

"Space Station Freedom:"



Space Station Freedom was a NASA project to construct a permanently manned Earth-orbiting space station in the 1980s. Although approved by then-president Ronald Reagan and announced in the 1984 State of the Union Address, Freedom was never constructed or completed as originally designed, and after several cutbacks, the project evolved into the International Space Station program.
http://en.wikipedia.org/wiki/Space_Station_Freedom

[Subjectivist]

The Case For Mars

http://youtu.be/30s3E1Z6-sg

[Sixstrings]

The Case For Mars

http://youtu.be/30s3E1Z6-sg

Thanks for the link, that looks good.

I know we've got to go forward with Mars, but I have to say I find Europa and Titan so much more interesting.

Titan is an alien world. "Same physics, unusual substances," as NASA says about it. It's got a thick atmosphere, oceans and lakes, wind and weather, massive sand dunes.

It looks so similar to weather on this planet, but yet everything is upside down.

The "rocks" are ice. All the H20 is frozen solid. The "oceans" are liquid methane and ethane. The "rain" is methane. The sand "dunes" are dirty ice particles, like coffee grounds.

Titan is cold, maybe not a great place for a colony, but not too hot like Venus anyhow, great view, fantastic scenery to look at -- you just can't take that space helmet off, you can't ever go swim in those oceans, they're methane.

Titan may have life -- the place has so much going on, it's a real chemical soup factory there.

NASA has joked that they ought to tell everyone about all the oceans of liquid nat gas on Titan, then NASA could get some funding. There would never be any "peak energy" problem on Titan, the whole place is a soup of hydrocarbons. And big, Titan is larger than the planet Mercury, and second largest moon in the solar system.

Then there's Europa -- not as interesting as Titan, but makes more sense and a calmer place -- ice cap, huge salt water ocean underneath, geo thermal vents.

You could stick an Ohio class submarine in the Europan ocean and it would do just fine. That salt water would split to oxygen same as ours does. The sub would run out of food, eventually, but who knows -- maybe there's fish and critters and plants to eat too in that ocean. We do not know, there could be, we won't know until a probe finally melts under the ice cap.

[Sixstrings]

Here's a video where someone recreated the canceled Constellation program (mars landing) in the game kerbal space program. "Duna" is "Mars," in the game:

I can't put in words how sad I am that the constellation missions got shelved. So I did a mission to Duna inspired by them
https://www.youtube.com/watch?v=Tp6yj2k0Fpc

If you're not familiar with KSP, it's a deeply complex simulation with a fun goofy angle to it, but the science is all hard science. Orbits, physics, gravity. Some JPL guys (real world rocket scientists) play KSP, one of them used it to test out a skycrane concept.

And NASA made an asteroid redirect mission, for the game.

This is a good documentary Subj linked, I'll bump it:

The Case For Mars

http://youtu.be/30s3E1Z6-sg

[Tanada]

SAN FRANCISCO — Life on Mars? Today? The notion may not be so far-fetched after all.

A year after reporting that NASA’s Curiosity rover had found no evidence of methane gas on Mars, all but dashing hopes that organisms might be living there now, scientists reversed themselves on Tuesday.

Curiosity has now recorded a burst of methane that lasted at least two months.

For now, scientists have just two possible explanations for the methane. One is that it is the waste product of certain living microbes.

“It is one of the few hypotheses that we can propose that we must consider as we go forward,” said John P. Grotzinger, the mission’s project scientist.

The scientists also reported that for the first time, they had confirmed the presence of carbon-based organic molecules in a rock sample. The so-called organics are not direct signs of life, past or present, but they lend weight to the possibility that Mars had the ingredients required for life, and may even still have them.

“This is really a great moment for the mission,” Dr. Grotzinger told a news conference here at the fall meeting of the American Geophysical Union.

http://www.nytimes.com/2014/12/17/scien ... -news&_r=1

[Sixstrings]

Interesting.. what could explain methane on Mars, other than life..

My prediction: there's some algae and microbes and stuff on Mars. Mars maybe have had more life back when it was green, with oceans and atmosphere.

And there has, of course, already been exchange of life between the two planets via asteroid impacts.

What we know from Earth: nature finds a way, to get there. Even the remotest island, something will drift to it, even the deepest lakes in the antarctic have life.

If simple life is deduced to be on Mars, then I'd say that raises the prospects for more complex life on Europa's oceans. Life may in fact be more common than we ever guessed, that's likely the case, since we know that planets do exchange life via asteroid impacts and also comets likely take life to other solar systems and it probably spreads all through the galactic ecosystem that way.

[Strummer]

You're forgetting radiation. Again.

[Keith_McClary]

There would never be any "peak energy" problem on Titan, the whole place is a soup of hydrocarbons.

You're joking, I hope.