We luckily avoided the clouds last night to see a big pink moon rise from Lake Superior. The moon languished near the horizon for a long time as if reluctant to meet the deck of clouds waiting for it higher up.
Watch for it to rise tonight about a half hour later. Will you be able to tell it’s no longer a perfect circle? A shadow has crept up along its western edge transforming it from a full to a waning gibbous moon.
Because the moon orbits Earth, we see it from a slightly different angle in relation to the sun each night, causing different parts of the globe to be in sunlight and shadow.
While you and I may prefer our dust swept away, planetary astronomers feel otherwise. Scientists at the European Planetary Science Conference (EPSC) in Lisbon, Portugal, recently got a look at photos of the first dust grains collected by Rosetta’s COSIMA instrument. The specks were gathered between August 11th and 24th from a distance of around 62 miles (100 km) from the nucleus of comet 67P/Churyumov-Gerasimenko.
Many tiny grains showed up on the plate; the two largest, each about the width of a human hair, stand out in the photo above. Some of the samples will be selected for further analysis on board the probe. Here’s how it works.
The target plate will be moved to place each selected grain under an ion gun, a device that blasts the particle with a beam of ions. Ions are atoms which have gained or lost an electron and become either positively or negatively charged. The ion beam will ablate or vaporize the grain layer by layer. The material is then analyzed in a secondary ion mass spectrometer to determine its composition.
Astronomers are quite excited about getting these early dust grains studied as they’re the first to be retrieved from the solar system’s “snow line”, the distance from the sun at which stable ice grains can form.
A new color-coded terrain map of 67P/C-G has also been created based depicting regional variations in the comet’s landscape. Some terrains are smooth, others dominated by cliffs and still others by craters and depressions. The maps will play a key role this weekend (Sept. 13-14) as Rosetta’s Lander Team and the Rosetta orbiter scientists determine primary and backup landing sites for the Philae lander.