Astronomy Picture of the Day

Explanation: The large Martian crater above just left of centre: is this a fresh crater, a degraded crater, or a ghost crater? Complex image recognition tasks like these are currently done more reliably by a human than a computer. Additionally, there are so many craters on Mars that NASA just doesn't have enough people to classify them all! Therefore, you can help humanity's understanding of the surface of Mars by volunteering to classify craters. All you need for this pilot study is a proper web browser and a mouse. If asked to classify the above crater, you might best respond that it appears relatively fresh, as it exhibits a sharp rim and a well-preserved interior. Degraded craters are typically older and have their rims more rounded, while "ghost craters" are the oldest of all and only faintly discernable.