MESSENGER News Thread, news, updates and discussion Options

[paxdan]

Launched on August 3rd 2004, NASA's MESSENGER will become the first spacecraft to orbit Mercury.

News and updates are availbale via Johns Hopkins University MESSENGER website and the Kennedy Space Center's MESSENGER website.

There will be an earth flyby in August followed by a couple of swings by Venus and three velocity scrubbing passages past mecury before the craft enters orbit in March 2011.

April 18, 2005 status report from JHU. Extensive JHU FAQs page here.

[Guest_BruceMoomaw_*]

Is Mercury's atmosphere similar to Moon rather than Mars? What is the composition of Mercury's atmosphere (hellium, hydrogen, oxygen, potassium and sodium)? Wiill the Messenger spacecraft  answer these questions?

It will indeed provide a great deal of additional information on Mercury's atmosphere -- which is incredibly rarified and thus similar to the Moon's atmosphere rather than Mars'. Indeed, both worlds actually have what is described as an "exosphere" -- from which the atoms and molecules escape almost immediately -- rather thann any stable atmosphere. Its surface density is only about one trillion atoms per cubic centimeter. (I'd have to look this up -- I haven't been following the discoveries regarding Mercury's atmosphere closely -- but I think this is an atmospheric density roughly a trillionth of Earth's.)

We also have confirmed recently that Mercury's exosphere contains small amounts of calcium. The exosphere seems to come from atoms "sputtered" off Mercury's surface rocks by the impacting atoms of the solar wind -- a phenomenon much more intense on Mercury than on the Moon, thanks to its closer proximity to the Sun -- and it is suspected that Mercury's magnetic field focuses this activity so that much of the sputtering occurs near the planet's poles.

Messenger's "Mercury Atmospheric and Surface Composition Spectrometer" really consists of two separate, entirely different instruments that might as well count as two separate experiments; they have little to do with each other. Its near-infrared spectrometer will map surface mineral composition, while its ultraviolet spectrometer will specialize in measuring the density, distribution and composition of the exosphere. (I don't know whether it can measure calcium, but I suspect it can -- and one of its goals will be to try to identify additional elements in the atmosphere, such as magnesium, silicon and sulfur.) Messenger's "Energetic Particle and Plasma Spectrometer" also has some ability to directly detect different elements' ions by mass spectrometry -- again, I'd have to do some digging for the details.

[Bob Shaw]

Bruce:

Can Messenger's instruments detect He on the surface of Mercury? I'm thinking of those old lunar He3 strip-mining plans...

Bob Shaw

[JRehling]

Bruce:

Can Messenger's instruments detect He on the surface of Mercury? I'm thinking of those old lunar He3 strip-mining plans...

Bob Shaw

In principle, He can be detected (quite easily, in fact), but that would only be if it existed in bulk concentrations, which it certainly will not. Lunar Prospector showed no He signal I'm aware of on the Moon. The quantity just isn't much to speak of.