mercoledì 10 giugno 2015

Ceres Bright Spots Keep Their Secret Even From 2,700 miles Up


Don’t get me wrong. I love this new photo. Dawn snapped it from its second mapping orbit from 2,700 miles up on June 6. The number of craters and the detail visible in the parallel troughs snaking through the scene are breathtaking. That’s why I hate to niggle about the white spots. While they appear larger and sharper than images taken in May from a greater distance, they’re too bright to show much new detail. I can’t help but wonder if mission scientists might adjust the exposure a bit the next time around. When photographing bright objects here on Earth, we expose “for the highlights” or the bright areas in photos to avoid overexposure and loss of detail. Naturally, when you try to capture details in something bright, your background will go dark. But that might be what’s needed here – a change in exposure to reveal more detail in the spots at the expense of the landscape. Doubtless NASA will release enlarged and detailed images of these enigmatic dots later this summer. Just call me impatient. Scientists still don’t understand the nature of the spot cluster, but reflective ice or salt remain the strongest possibilities. “The bright spots in this configuration make Ceres unique from anything we’ve seen before in the solar system,” said Chris Russell, principal investigator for the Dawn mission. “The science team is working to understand their source. Reflection from ice is the leading candidate in my mind, but the team continues to consider alternate possibilities, such as salt.” It’s interesting to compare and contrast Ceres with Dawn’s first target asteroid, Vesta. Craters of every size dominate both small worlds, but Ceres shows evidence of a more activity in the form of relaxed crater rims (possibly due to ice deformation), landslides and collapsed structures. FONTE: universetoday