MESSENGER

[Mjolnir]

Just a heads up...MESSENGER is to enter orbit around Mercury on the 18th, just 10 days from now. It's been a long trip...

[Trantor]

Just a heads up...MESSENGER is to enter orbit around Mercury on the 18th, just 10 days from now. It's been a long trip...

About the same amount of time it took Cassini to reach far more distant Saturn. Celestial mechanics, fascinating.

[Mjolnir]

Just a heads up...MESSENGER is to enter orbit around Mercury on the 18th, just 10 days from now. It's been a long trip...

About the same amount of time it took Cassini to reach far more distant Saturn. Celestial mechanics, fascinating.

And New Horizons zipped past Saturn orbit on its way to Pluto in just a couple years, ending its last burn with 16.26 km/s relative to Earth...in a different direction, that could put it in an elliptical orbit between 0.1 AU and 1 AU. Split across two burns in a direct Hohmann transfer, it would have fallen just short of Mercury's orbit around the sun, but gotten there in a couple months. To get to the sun itself (always quite close to 1 AU away), it would have to take an indirect approach...looping out to Jupiter and using its gravity well to change direction, perhaps. Or cheating and using a solar sail.

With the gravity well of Mars to catch you and their own shallower gravity wells, the surfaces of Phobos and Deimos are easier to reach than that of our own moon. The moons of Jupiter are similarly easy to get to, even without taking the Oberth effect in Jupiter's gravity well into account...

[Arioch]

And New Horizons zipped past Saturn orbit on its way to Pluto in just a couple years

Yeah, it's already crossing Uranus orbit. Hard to believe half the 9-year mission is already gone... how time flies...

[icekatze]

hi hi

That is very cool, looking at the photos Messenger sent back from its flybys, it got me thinking about the feasibility of building facilities on a close, tide locked planet like Mercury. With all those craters, there are lots of places that are covered in shadow even as you move away from the terminator.

(The mission that I'm following with lots of enthusiasm is the Dawn mission. I know Vesta doesn't have a huge gravity well, but I still think it is cool that the probe is going to go into orbit and then break orbit again before moving onto its next target)

[Mjolnir]

That is very cool, looking at the photos Messenger sent back from its flybys, it got me thinking about the feasibility of building facilities on a close, tide locked planet like Mercury. With all those craters, there are lots of places that are covered in shadow even as you move away from the terminator.

Not sure if you meant to imply that Mercury was tidally locked....it's actually in a 3:2 spin-orbit resonance. There's lots of permanently shadowed areas at the poles, though, and apparently plenty of ices. Delta-v to get there from Earth is high, but solar sails are more effective for trips to and from it. And of course, there's plenty of solar power. Its surface gravity is slightly higher than that of Mars, but its gravity well is smaller and the lack of an atmosphere makes use of rocket landings easier (the atmosphere of Mars is thin enough that powered landings are needed for large payloads, but getting stable operation from rockets pointed into a hypersonic airstream is...difficult). The worst difficulty is solar radiation on the trips to and from it.

(The mission that I'm following with lots of enthusiasm is the Dawn mission. I know Vesta doesn't have a huge gravity well, but I still think it is cool that the probe is going to go into orbit and then break orbit again before moving onto its next target)

Indeed...it reaches Vesta this July and stays for a year. I'm particularly interested in Ceres (which is almost a scale model of a planet and may have an ocean of liquid water), which it won't reach until February 2015...but we're finally getting a close look at two of the largest asteroid belt objects!

[icekatze]

hi hi

Huh, I guess my elementary school education was not entirely accurate. Kind of impressive that I was able to go that long without realizing it. Still, being able to see the topography in relief was a big eye opener. I never really got an impression of the scale of things by those little thumbnail pictures that I had seen previously.

Ceres really is the big prize, honestly I'm amazed by how few people even know of its existence. Even if Ceres doesn't have liquid water, it almost certainly has water in the form of ice. If anyone ever got to the point of mining the asteroid belt, I could see it being a prime piece of real estate. Though I couldn't speculate at the feasibility of that idea with too much certainty.

[Karst45]

Its surface gravity is slightly higher than that of Mars, but its gravity well is smaller

I thought that the surface gravity and the size of the gravity well would be related. how is that possible?

Ceres really is the big prize, honestly I'm amazed by how few people even know of its existence. Even if Ceres doesn't have liquid water, it almost certainly has water in the form of ice.

Well I knew about that "moon" but didn't actually knew the name. What amazing with that is if there a liquid ocean there the possibility of microscopic life form if not well... there water. To bad there is no petroleum there or our space exploration would be on turbo

[Mjolnir]

I thought that the surface gravity and the size of the gravity well would be related. how is that possible?

Mercury has less mass but notably higher density...more of it is iron rather than rock. Saturn has just over 1 g of "surface" gravity despite having 95 times the mass of Earth. Neptune has slightly higher surface gravity than Saturn, about 1.1 g, despite only having 17 times the mass of Earth...it's got more ices and less hydrogen and helium.

Well I knew about that "moon" but didn't actually knew the name. What amazing with that is if there a liquid ocean there the possibility of microscopic life form if not well... there water. To bad there is no petroleum there or our space exploration would be on turbo ;)

Ceres isn't a moon, it's a dwarf planet, recently upgraded from "asteroid". I suspect you're thinking of Europa, though Ganymede and Callisto (around Jupiter) are also thought to be decent candidates for liquid oceans, and possibly Titan (a moon of Saturn).

[Karst45]

I think ill have to retake class on space body, mass isnt the "gross weight without the gravity effect? thus would include the density? Or is mass, in this case, a synonym of "planet size"

Ceres isn't a moon, it's a dwarf planet, recently upgraded from "asteroid". I suspect you're thinking of Europa, though Ganymede and Callisto (around Jupiter) are also thought to be decent candidates for liquid oceans, and possibly Titan (a moon of Saturn).

I think titan was the planet i mistook for Ceres.

From the Wiki we discovered it in the early 1800. why isnt it studied in basic astronomy? we learn about all the other planet (i wont give a number cause they kind of changed all that 2-3 year ago so i don't know what number is true now) why not talk about this one?

[Mjolnir]

I think ill have to retake class on space body, mass isnt the "gross weight without the gravity effect? thus would include the density? Or is mass, in this case, a synonym of "planet size"

Mass is just mass. The attribute of matter measured on a balance. Gravity is proportional to mass and inversely proportional to the square of distance, higher density planets pack their mass into a smaller volume and put their surfaces at a shorter distance from their mass.

I think titan was the planet i mistook for Ceres.

Titan's a moon. ;)

From the Wiki we discovered it in the early 1800. why isnt it studied in basic astronomy? we learn about all the other planet (i wont give a number cause they kind of changed all that 2-3 year ago so i don't know what number is true now) why not talk about this one?

Which one? And they were all at least mentioned in my science classes...

[Karst45]

From the Wiki we discovered it in the early 1800. why isnt it studied in basic astronomy? we learn about all the other planet (i wont give a number cause they kind of changed all that 2-3 year ago so i don't know what number is true now) why not talk about this one?

Which one? And they were all at least mentioned in my science classes...

Well Ceres.

Suppose my science classes werent up to date.

[icekatze]

hi hi

My elementary education was at about the same level as The Magic Schoolbus, as far as in-depth information was concerned. When we came back to the topic in Earth Sciences in high school, we did the entire astronomy section from the perspective of a backyard telescope; recognizing constellations, determining where certain stars would be at what time of year, etc.

[Trantor]

Live view from earth:



About 40 minutes after sunset, to the west.
Now we just need eyes with better resolution.

[Karst45]

Live view from earth:



About 40 minutes after sunset, to the west.
Now we just need eyes with better resolution.

what you dont have cyber eyes yet? Poke your eyes out and get upgraded now!

[Mjolnir]

http://www.planetary.org/blog/article/00002956/

And a handy time converter: http://www.timeanddate.com/worldclock/c ... sec=0&p1=0

[icekatze]

hi hi

I just saw this cool flyby video of saturn, I wonder if someone is going to make one for mercury.

[Mjolnir]

One hour to Mercury orbit.
http://www.dmuller.net/spaceflight/real ... =messenger
http://messenger.jhuapl.edu/mer_orbit.html

[Mjolnir]

MESSENGER entered orbit as planned. The burn looked perfect. Now we can get a close look at the poles...and those volcanos, and the core and magnetic field...

[GeoModder]

...and finally map the whole planet (in detail)...