This week's question:

When was the first recorded observation of Mercury’s transit across the sun, and who made that observation?

To submit your answer:

Complete the contest entry form at http://planetary.org/radiocontest or write to us at [email protected] no later than Tuesday, May 3rd at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

What is the name of 90482 Orcus’ moon?

Answer:

The answer will be revealed next week.

Question from the week before:

What moon in our solar system has a massive equatorial ridge running three quarters of the way around it?

Answer:

Saturn’s moon Iapetus has a massive ridge running three-fourths of the way around its equator.