Mercury

1.Closest planet to the sun, smallest planet in the universe (if you don't count Pluto). Oldest surface and least explore planet.

2. .387 AU from the sun (earth is 1), mass is .055 of Earths, and gravity would make a 100 pound person on earth only weigh 38 pounds on Mercury.

3. Mercury is so close to sun that Hubble can't look at it cause the solar light overwhelm and damage Hubble.