How life formed on Earth remains a mystery—meanwhile, scientists are still wondering whether life ever existed on Mars. The first photo in this week's roundup could harbor clues to both. Captured by NASA's Mars Reconnaissance Orbiter, the image reveals a swath of Martian terrain covered in deposits that may have formed when volcanic activity combined with standing water—conditions similar to those on Earth, when early life was evolving here.

Next, in the spirit of spooky season, is an eerie photo of star clusters swarming a massive galaxy named NGC 4874. Its gravitational pull is strong enough to attract more than 30,000 globular clusters of stars—more than any known galaxy.

Back in our own solar system, a photo taken by the European Space Agency's Mars Express orbiter resembles areas of home. An impact crater on the red planet has been collecting wind-swept materials and creating picturesque dunes inside the depression.

Also on Mars—or around Mars, rather—NASA's Mars Odyssey orbiter imaged Phobos, one the red planet's moons, in infrared. The potato shaped moon's varying surface temperatures are depicted here by a range of colors.

Finally, the true star of this week’s photo series is the sun. The European Space Agency's astronomy club took an amazing photo of a bird and the International Space Station passing before Earth's parent star, creating an X-mark.

Want more photos of this wondrous universe? Then check out the entire collection.