Topic: Modest space project idea: Lets make a planet.

[Sirgod]

sorry Storm, I've got to Get some sleep.  let's take this up tomorrow Morning If we can.

Stephen

[Stormbringer]

Well jupiter would likely explode if it spun any faster. It is already deformed radically from it's very fast spin. Spinning would not increase it's mass (you are thinking of inertia). And even if it did it would not affect the variables we want to manipulate. In fact increasing jupiters mass, if it was possible, might ignite nuclear fusion and create a short lived star.

The question about tidal forces was in the event Integerspin is correct and a planet cannot form in the asteroid zone due to jupiter's gravity interactions. I was considering parking the planet in an established orbit like that of Mars or even the Earth. Baring tidal problems if they were at the same speed in the orbit on opposite sides of the ellipse they would never collide. I was asking about tidal and gravitic induced tectonic damage, earthquakes, volcanoes; that sort of thing.

I do not know enough to know if that is a safe idea. If it was and enough material could be found we could build multiple Earth-like planets and solve all sorts of humanities problems for millenia to come.

[IntgrSpin]

Quote:
isn't it also possible that those unfavorable conditions abated as the solar system matured but the dust was blown out by the solar wind and the critical mass or density is not there to restart the planetary formation process naturally by gravitic accretion. An artificial push might restart it?

Sure. Near as I can remember, there is something like the mass of 2/3 of the moon in the asteroid belt currently. I'd look it up though, because I don't really remember.

Quote:
Spinning would not increase it's mass (you are thinking of inertia).

Actually it does, a teeny weeny bit.  

Quote:
I was asking about tidal and gravitic induced tectonic damage, earthquakes, volcanoes; that sort of thing.

Gravity is weak enough that you needn't worry. If you think about it, we periodically come closer to Mars and Venus than we ever could to a 'trojan planet'.

My take on the thing is that in the beginning, we're going to be too busy not dying out there to be worried much about 'contaminating' the solar system (much like the New World in the 1500's). By the time we start to worry about preserving pristine extra-terrestrial environments, we'll probably have a McDonalds on Mimas.  


   

[Stormbringer]

Is that determined by direct observation or by measuring tidal perturbations in planet and asteroid movement? It seems low. The amount of dust that was blown away would be many many times what is left if that is the case. But even if it is correct the kuiper belt has some mass that is not ice or hydrocarbon. Beyond that is the Oort cloud and the escaped dust mentioned earlier.

If it weren't for the outcry that would ensue I'd just drop the load of asteroids on Mars to increase it's mass and thus gravity. The proper atmosphere could then be held. The oxygen and nitrogen would not escape. Water vapor would be held the temperature would increase. Planetary ice fields would melt. The hydrocycle would heat up. Greenhouse effect would become self reinforcing. Weather would develop including thunderstorms with lightning and ozone would naturally develop.  Unfortunately that would be stymied for centuries as the ethics of the situation were endlessly debated.  

[IntgrSpin]

I threw "mass asteroid belt" into google and got some hits. This from Minnesota State,

http://www.mankato.msus.edu/emuseum/information/solarsystem/asteroid_belt.html

Quote:
Asteroids are small, rocky, irregular bodies orbiting the sun. The first asteroid was discovered by Giuseppe Piazzi in 1801. He originally thought he had found a comet, but found that its orbit more closely matched those of planets rather than comets. He named the object Ceres. Ceres is the largest of all known asteroids. It is 933 km in diameter and contains about 25% of the mass of all the asteroids. The asteroids together have a mass less than that of the Moon.

The majority of the known asteroids exist between Mars and Jupiter. This area contains over 4,000 numbered bodies. This area is unique because the asteroids did not form a planet. Jupiter's early formation may have affected this area by either sweeping up or ejecting many of the bodies.

Asteroids within the asteroid belt, or Main Belt asteroids are divided into subgroups named after the main asteroid of the subgroup. Asteroids not within the Main Belt are either Near Earth Asteroids or Trojans, which are asteroids near Jupiter

I have no idea how the mass was determined.

It is true that the molecules in the atmosphere form a Maxwell distribution, and molecules that end up in the high speed tail will escape. However, even for a planet the size of Mars, the time for the average molecule to escape would probably be low enough that if you put an Earth-sized atmosphere around Mars, it would probably keep it for several hundred million years (assuming it was also kept abnormally hot... for us). You can probably figure it out yourself. Get the mass of Mars, figure out what the escape velocity is, pick a mean average temperature, and apply a Maxwell-Boltzmann distribution. Assume that we can live with the atmosphese depleting to 75% of whatever we start with (maybe choose sea level on Earth as a base), and solve for t. I'd be surprised if it wasn't several hundred million years.

 

[Stormbringer]

My understanding is that molecules at the very outer edge of the atmosphere are dislodged from the weak gravity holding them there by everything from brownian collisions, cosmic ray collisions, solar wind, photon pressure, meteor and other macro-body impacts and even thermal motion. Mars gravity, at a mere 33% of earth's allows far more of this loss than higher gravity worlds such as Earth. During the close study of mars evidence that Mar's atmosphere was much thicker and had far more water nitrogen and oxygen than it does now. and most of that atmosphere was lost to space. Some ended up bound in the rock and ice. For example there is a lot of oxygen in the form of rust or oxide compounds which give a red tint to the planet. Mars current atmospheric pressure is nearly a vacuum and what little is there is unbreathable even if the pressure was greater.

This data is why I assume a larger Mass would be needed to ensure Mars could retain  a breathable and radiation shielding atmosphere. That supposition may be false but more mass would also increase the gravity which would make humans more at home and allow for returning to Earth for people who had been there for some time or were even born there.

[IntgrSpin]

For the hell of it, I did the calculation. I got about ~5000 m/s for the Mars escape velocity, and assumed the atmosphere was exclusively oxygen. From 1 atm to 0.75 atm, at a mean temp of 15C, t=26 million years.

I thought this was kinda low, but then remembered that our atmosphere is constantly being replenished. Still... 26 million years isn't too bad.    

[Stormbringer]

No it's not bad at all. My sin is conflating brief periods of time on a cosmic scale with brier periods of time in human scales.[IIRC that is about the amount of time the planetary scientist said it took for it to lose the old atmosphere minus major impact ejections ( evidence of which includes martian origined meteorite found on earth)]


I still need to bomb the planet with comets  though. It is the only way to get a suitable atmosphere in acceptable human time scales. The other methods are far to slow. Genetically engineered microbes to free the bound oxygen from the soil, Lichens to absorb heat and warm the polar ice and permafrost would take 100s of thousands of years if not millions of years. Most of earths early oxygen supply cam from photo-plankton in the oceans which Mars lacks. They could do it faster but still to slow for waiting colonists. And with the vacuum like conditions and sublimation the supporting layers would not form (ozone and similar layers.) And I would still like the gravity to be as near Earth's as possible. So I might need to rain asteroid bits on the planet as well.

Perhaps I am just violent.

[IntgrSpin]

Maybe we should send all our Ford Expiditions up there.    

[Stormbringer]

All SUVs.  

[Stormbringer]

Another bad thing about mars is there is no magnetosphere and the cosmic ray dose rate would be twice what is is in the ISS. Shielding would be necessary unless The atmosphere created would stop enough of it. The added mass would likely cause the break up of the crust and restart both tectonic migration and convection celles in the core to mantel region. This would create a magnetosphere.

[Sethan]

Erm... won't significantly increasing the mass of Mars (to increase the gravity) also change the orbit of the planet?

[Stormbringer]

It might.  gravitic equations, force equations, orbital mechanics all have mass components. However by carefully controlling the vector that the new mass is moved along as it is being applied to the base mass it should be possible to keep the orbit constant by altering the orbital velocity at the same time. do you see what I am talking about or do I need to elaborate to clarify the idea? As an aside a minor alteration in orbital elipse size would not present to large a problem. we don't want the planet carooming off into space or colliding with another planet.


As an aside there is a panned but generally accurate rule of thumb for orbital distance known as Bode's law that accurately predicts the location of planets in the solar system. It may be that planets are compelled somehow to assume these orbits or be cast out. There is some unkown but natural phenomenon at work behind Bode's correlation.

[Sethan]

Storm, if you're talking about slamming these masses into the planet at high enough speeds to significantly affect the orbital velocity, you're talking about doing very bad things to the planet itself.  The trick would be in not ending up with a second asteroid belt.

[Stormbringer]

No, the asteroids would be processed down to manageable non planet busting size set on a path to collide with a specific region of the planet and imparted with a proper incremental velocity. We do want some stress to the planet but not eough to shatter it.Tectonic activity on Mars has all but ceased. so has convection in the interior. That is why there is no magnetosphere. you could alter the planets vector with B B's if you used enough of them. By striking from different sides at different points along the orbit we can slow the orbit enough to maintain its orbital path.If the orbit is not in danger then the rest of the asteroid mass can be added as micrometeorites. there will be thousands of little turing machines carrying out that work. Any orbit shifting needed will be handled further out by specialized machines which can do the proper analysis.  

[Sethan]

Why am I reminded of the most recent incarnation of the movie version of The Time Machine, and what happened to the moon?

Sounds great as long as it works like you plan it to.

[Stormbringer]

Of course, Newton worked out the equations that explain how planets orbits can be determined. Before anything like this would be attempted it would be modeled to death. Each gram could be modeled for what effects it would have. Tons of space dust land on the earth each day. We have yet to spiral into the sun or zoom off into space. We have been struck by impactors large enough to kill off almost 90 percent of all lifeforms at least three times.  There are craters so huge that we could not detect them except from space. The planet is still here in a stable orbit. I'm not even sure that the mass change would significantly affect the orbit of the planet unless we designed the impacts to have that effect. If that is the case the equations would immediately tell us of any such danger and modeling certainly would. They might tell us to just dump the asteroid dust evenly on the surface. I might do the math this weekend. If so, I'll let you know. I'd feel better if one of our engineer or scientist friends did it though even if the equations are straight forward.  

[Sethan]

Quote:
Of course, Newton worked out the equations that explain how planets orbits can be determined. Before anything like this would be attempted it would be modeled to death. Each gram could be modeled for what effects it would have. Tons of space dust land on the earth each day. We have yet to spiral into the sun or zoom off into space. We have been struck by impactors large enough to kill off almost 90 percent of all lifeforms at least three times.  There are craters so huge that we could not detect them except from space. The planet is still here in a stable orbit.  

All true, Storm - but you are talking about adding enough mass to increase the planet's gravity by 150%.  That's gonna make a difference.

[Stormbringer]

I will work the equations for a mars sized planet at mars orbit and an earth sized planet in the same orbit then I'll *try* a vector equation based on mars being struck by various masses, velocities and directions. My bet is the size would have to be huge for it to do anything from a single impact whether that something is destroying the planet or flinging it away. Too bad I cannot post scientific formula symbols here.  

[Stormbringer]

This is relevant because it has to do with orbital mechanics for various mass terrestrial planets. Also because it says terrestrial planets are common.

Earth-Like Planets Common, Computer Simulation Suggests
By Robert Roy Britt
Senior Science Writer
posted: 02:51 pm ET
11 December 2003

 

A new computer model designed to explore the range of possibilities for planet formation around other stars had no trouble coming up with worlds similar to Earth.  
 
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The simulations generated planets in similar orbits, planets with and without water, and a range of other virtual places that resemble Earth and the other inner, rocky planets.

The effort was designed to determine whether the four inner planets in our solar system, called terrestrials, represent a typical or extreme evolutionary scenario compared to what might develop around a Sun-like star with slightly different dynamics, explained said Sean Raymond, a University of Washington doctoral student in astronomy.

"We found there's a much wider possible range of masses and water content on terrestrial planets," Raymond said in a telephone interview.

"You can have planets that are half the size of Earth and are very dry, like Mars, or you can have planets like Earth, or you can have planets three times bigger than Earth, with perhaps 10 times more water," Raymond said.

Raymond worked with Thomas Quinn, an associate astronomy professor at the university, and Jonathan Lunine, a professor of planetary science and physics at the University of Arizona. Their results, announced today, will be published in the journal Icarus.

Behind the simulations

Astronomers have found more than 100 planets around other stars. All are at least as massive as Saturn and not the sorts of places where intelligent life is likely to flourish. But theorists are using what they've seen as a springboard for imagining what might lurk undiscovered within those systems. A handful are, mathematically, capable of supporting Earth-mass planets in Earth-like orbits.

The new model considered what sorts of rocky planets might form around a star with a known giant planet. The simulations represent the extremes of what is possible, the researchers say, and so it's not known which of them might represent reality.

There is just one giant planet in each of 44 simulations. The model makes an assumption that a giant planet forms quickly, before terrestrials. (Theorists have not determined whether or not that is how things happened in our solar system.) Gravity-based formulas are put in place and time is allowed to evolve. Virtual small rocks collide and stick and eventually form terrestrial planets.

In some cases the initial planet contains the mass of Jupiter, in others it's weightier. Its orbit is like Jupiter's one time, much more elliptical the next.

The validity of the model is suggested by the fact that when the virtual Jupiter takes on characteristics similar to the real Jupiter, a set of inner planets similar to those in our solar system tends to develop.

However, Raymond said, very minor adjustments to the starting conditions fueled wildly different outcomes.

One simulation generated just one terrestrial planet, a whopper up to four times as massive as Earth with up to half again as much water. In another model, five small terrestrials were born, but all were significantly smaller than Earth.

At least one terrestrial planet of some sort was spawned by each scenario.

Key to life: Water

One goal of the study was to determine whether habitable planets might be a common development around other stars. Scientists agree that water is the primary key to life as we know it. Water on the virtual worlds turned out to be dependent on the orbit of the outer, giant planet.

Non-circular routes, called eccentric orbits, are bad news.

"The more eccentric giant planet orbits result in drier terrestrial planets," Raymond said. "Conversely, more circular giant planet orbits mean wetter terrestrial planets."

Here's why: A giant planet in a circular orbit tends to send water-laden asteroids inward, where some of them strike the terrestrial planets and deliver the water. Giant planets orbiting eccentrically tend to kick asteroids outward.

Earth is thought to have been dry when it formed. Water, theorists think, was delivered later by asteroids or comets, which formed farther from the Sun where water could be retained, Raymond said.

In the case of our solar system, Jupiter's orbit is slightly elliptical. The researchers said this middle-of-the-road, real-world scenario could explain why Earth is not a total waterworld nor a complete desert.