[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]
And if I can be shameless: Forbes pays according to traffic, so the more of you who share and visit and read my stuff, the better they pay me. Ahem.
The orbit of Mercury, including effects from general relativity and other planets in the Solar System. I’ve exaggerated the effect for easy viewing; in real life, the orbit is very nearly an ellipse. [Credit: Matthew R Francis]
Despite the discovery of other galaxies, black holes and other marvelous astronomical bodies, we keep returning to the orbits of planets to understand gravity at its most basic. Partly that’s simplicity: We’re inside the Solar System and can make measurements without spending billions of dollars or building virtual observatories the size of the whole planet. But that doesn’t mean we’ve exhausted all the ways to learn about gravity from the dance of the planets.
In a new paper in Physical Review Letters, University of Florida physicist Clifford Will showed that the upcoming BepiColombo space probe may be able to test an aspect of Albert Einstein’s theory of gravity, general relativity, that’s been out of reach so far. This effect comes from the gravity of other planets in the Solar System, leading to a tiny shift in Mercury’s orbit. But small doesn’t mean unimportant: If general relativity needs to be modified on this tiny level, the BepiColombo probe may be able to spot that discrepancy.
[Read the rest at Forbes…]
The MESSENGER (MErcury Surface Space ENvironment, GEochemistry, and Ranging) spacecraft has found strong evidence both for water ice and organic molecules in shadowed craters near Mercury’s poles. Unlike Earth, Mercury has no seasons: its axis stands perpendicular to its plane of orbit, so deep craters near the north and south pole will have bottoms in permanent shade. Any place else on the surface will eventually be exposed to the Sun’s punishing glare, not only melting ice but boiling away any residual water. However, during the early Solar System, meteorites and comets brought water and organic compounds to the planet’s surface—at least according to planet formation models. This new discovery lends strong support to that theory.
The results from both the reflection and neutron analyses were consistent: several craters in Mercury’s polar regions provide sufficient shadow for stable water ice. The large craters named Prokofiev and Kandinsky were both found to contain significant radar-bright (RB) patches, indicating highly reflective materials. (Craters on Mercury are commonly named for famous artists, authors, composers, and the like. As a fan of both Prokofiev and Kandinsky, I approve.)
The size of the reflective patches matched the total proportion of each crater that lies in permanent shadow. [Read more…]