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Messenger En Route To Mercury
Soft writes "NASA's Messenger space probe has lifted off on its second try on a Delta 2-Heavy rocket.
As mentioned earlier on Slashdot, it is poised to orbit Mercury in 2011 after three flybys, as well as two flybys of Venus and one of Earth for course corrections.
It will be the first probe to visit the innermost planet since Mariner 10 in 1974 and 1975.
Stories on the BBC and SpaceflightNow."
Mercury is real hard to observe from Earth-based telescopes since it is so close to the Sun. In the near future, the only way to get higher resolution data is to send the telescopes to Mercury. Even the most fervent remote sensing advocate will have to admit that data quality generally improves with decreasing distance to the target.
Using martian studies as an analogy for mercurian (hermitian?) observations, one can see how spacecraft data provide much more detailed observations over ground-based observations. Earth-based data of Mars obtained during the last opposition last summer (when Mars was closer to Earth than Mercury ever gets) does not compare to spacecraft data in terms of resolution. Earth-based (visible-wavelength) observers of Mars have to content themselves with seeing albedo variations. The geology which caused those albedo variations was largely unknown prior to our sending spacecraft. (Please note that tha "canals" reported by Lowell were likely optical illusions - Lowell's canal maps do not correspond to locations of known martian dry channels.)
Similarly, Earth-based spectroscopic observations of Mars have poor spatial resolutions. I remember one paper from '96 which reported 300 km/pixel resolutions. Two spectrometers currently in orbit around Mars get far better spatialresolution (Thermal Emission Spectrometer gets 3 km/pixel; THEMIS-IR gets 100 m/pixel - although, granted, that's with a low spectral resolution).
Two advantages that Earth-based observations have over spacecraft data are: 1) Earth-based observations are a lot cheaper to obtain and 2) a network of Earth-based observers can look for changes in the target with better time continuity than a singe spacecraft (since the spacecraft may be looking at some other part of the planet).
The true value of a Mercury mission is two-fold. Most obviously, new spacecraft observations will provide geologic context for current ground based observations (Mariner 10 only imaged ~40% of the planet). Additionally, Mercury is considered an end-member planet - a planet that likely formed close to the Sun in the solar nebula from which the solar system formed. As such, understanding how Mercury formed will provide a calibration point for models of solar system formation, which could have implications for formation in other portions of the solar nebula or the early solar system or of other planetary systems.
No, we aren't going to be sending people to Mercury anytime soon, but neither are we going to be sending people to Mars in the near future. (Even Bush's space initiative doesn't plan a Mars landing for at least 20 years - plenty of time to get distracted by other problems.) However, even if people aren't going to those placed, there are still useful things to learn regarding the solar system in which we live.