Venus Probe Set to Reach Target 141
Accommodate Students writes "The BBC is reporting on the first space mission to Venus in a decade, which is about to reach its target. From the article: 'On Tuesday morning, a European robotic craft will perform a 50-minute-long engine burn to slow its speed enough to be captured by Venus' gravity. Venus Express will orbit our nearest planetary neighbour for about 500 Earth days to study its atmosphere, which has undergone runaway greenhouse warming.' If all goes well, it could shed important light on climate change here on Earth."
Moons (Score:1, Interesting)
From TFA:
Moons venus: 0 earth: 1I remember an old theory that the moon keeps Earth from boiling over by sweeping away much of the atmosphere over time. I wonder if this is still considered a significant factor?
Its worth noting that the moons of Mars are in much lower orbits than our moon, and mars has much less of an atmosphere than earth.
Re:Moons (Score:5, Interesting)
I've heard the same thing... in science fiction novels. Larry Niven, I believe. It may be true, but I've never seen any comprehensive explanation of how this is supposed to occur. Does the atmosphere somehow leak away on geological timescales through the Lagrange points somehow? I've got no idea. Does anyone know?
This idea does appeal to me, though, because if true it adds another factor to the Drake equation for finding *earthlike* civilizations in the galaxy. According to the impactor theory of the moon's origin, the moon's creation was a very improbable event. Perhaps that's why we don't see any Dyson spheres- you not only need a planet in the liquid water region of a solar system, you need that planet to be whacked at a very particular angle to form a moon large enough to prevent a Venus from forming instead of an Earth.
Its worth noting that the moons of Mars are in much lower orbits than our moon, and mars has much less of an atmosphere than earth.
It's also worth noting that Mars' moons are TINY. Phoebos and Deimos are 22 and 12 km in diameter, respectively. They're utterly insignificant.
Compare that to the Moon, which is comparable to Earth in both diameter (27% of the earth's) and to a lesser extent mass (1.2% of the earth's). In fact, some astronomers consider the Earth-moon system to be a double planet because of this fact.
Re:Moons (Score:4, Interesting)
No, but the Moon did slow down the rotation of the Earth by quite a bit. If Luna'd be lacking, Earth's surfaces would supposedly be battered by extremely strong winds.
It's theorised that Venus' climate isn't caused by its lack of a moon but because it's rotating way too slow (I got the climate-link from Stephen Baxter's Space, but I'm sure it's well documented in astronomic science). It takes about 243 days for Venus to rotate around its axis, and it's even rotating in the opposite direction as most of the rest of the (Sol system) planets.
Bacterial life in the clouds? (Score:3, Interesting)
I wonder of Venus Express will ever sample the Venusian atmosphere to see -- perhaps as an "Extended Extended Mission" as they deorbit the probe years from now.
Possibility of Life? (Score:2, Interesting)
Global warming, beside the point (Score:2, Interesting)
Yet global warming is a fact, no-one disputes that (anymore). What are we going to do about it? In addition, oil is going to become harder and harder to extract. It IS a finite resource.
Right now we are looking at massive future crop failures. Massive hunger even in western countries.
Large scale flooding of important cities and centers of production, disruption to transportation and communication.
We should be planning for these, stockpiling food, re-thinking food production, massively reducing oil consumption (we'll need it later) and building flood protection.
The POINT is, none of this is POLITICALLY, or more importantly ECONOMICALLY possible right now.
And that is what we should be worrying about right now.
Re:Moons (Score:3, Interesting)
When that huge impact happened, what was blown off was most of the lighter, surface material of the early Earth. All of those light silicates eventually clumped up to form the moon, leaving a body with a much thinner crust and a higher overall proportion of heavy metals. This made it much easier for convection currents to run inside the Earth's core, allowing the creation of a magnetic field. This deflected the solar wind, protecting the Earth from most of the hard radiation from the Sun. Venus doesn't have much in the way of protection: [ucla.edu] It's the moon pulling on the Earth that keeps this "stirring" going, by tugging on the surface and slowing it at a faster rate than the core.
The relatively thin crust made it much easier for the surface to crack and float around in pieces. If it were really thick, like on Venus, it would be too rigid for easy cracking, bumping, and grinding. Plate tectonics causes a lot of carbon on the surface to be sucked under the surface and recycled.
Tidal forces caused by the moon also pulled on the early Earth atmosphere, causing it to expand upward beyond the protection of the magnetic field. Once up there, the gases were swept away.
An aside on moons (Score:2, Interesting)
Years ago, Isaac Asimov wrote an article called Just Mooning Around that I read in a collection called Of Time and Space and Other Things.
In the article, Asimov calculated what he called the "tug-of-war ratio" for a particular satellite: the ratio of the sun's pull on a satellite to the primary's pull on that satellite. For Jupiter's satellites, for example, the Galilean moons are pulled much more strongly by Jupiter than by the Sun, whereas with the outer satellites Jupiter just barely wins the contest, making it likely that they are captured asteroids.
He goes on to calculate a maximum distance at which each planet is able to hold satellites. This gets interesting in the inner solar system. Mars' "tug-of-war distance" is just beyond where its two tiny moons happen to exist; Venus' maximum satellite distance is within its atmoshpere; and Mercury's maximum distance is beneath its surface. The Earth, of course, has no natural satellites within its maximum calculated distance.
So what's up with our Moon? At a quarter of a million miles away from us, the Sun pulls our Moon more than twice as strongly as the Earth does. Therefore, Asimov speculates, the Moon is not a true satellite of the Earth. He says that if you were to draw the Moon's orbit to scale, it would always be concave toward the Sun, and concludes that the Earth and the Moon are a binary planet system.
So the reason Venus has no moons is because it can't... then again the Earth can't have the moon it does either, but it managed to cheat somehow.
Re:Slow Rotation of Venus / Temperature of Dark Si (Score:3, Interesting)
Wikipedia [wikipedia.org] mentions min/mean/max surface temperatures of -45.15 degC, 463.85 degC and 499.85 degC (-49.27 degF, 866.93 degF and 931.73 degF) respectively.
Only if you're interested in a semi-nomadic lifestyle.
There have been proposals to establish human colonies in the cloudtops of Venus, which are much more livable temperature- and pressure-wise. These would have the advantage of being relatively easily movable so as to remain optimally positioned.