Maxwell is accompany the astronaut to space again. To make peace with the alien, he can offer alien the following:

Round 1: President
Round 2: Ambassador
Round 3: Gift

As Maxwell is permitted to set up a new human colony, first requires a water source:

Round 1: Rain (storm)
Round 2: River
Round 3: Pond

Then, he needs to create three food sources:

Round 1: banana, apple, cow
Round 2: grape, goat, chicken (bird)
Round 3: pig, ox, pineapple

Last, he needs to create a renewable source of oxygen:

Round 1: oxygen tank
Round 2: tree
Round 3: grass

Scribblenauts Remix 11-1 Cheats Hints gallery:
11-1-1-a: Make peace with the alien!
11-1-1-b: Give the alien a peace offering.
11-1-1-c: Create an ambassador from earth.

11-1-2-a: A new human colony requires a water source!
11-1-2-b: The water source must be renewable.
11-1-2-c: Create a naturally occurring body of water.

11-1-3-a: Create three food sources for the new colony!
11-1-3-b: Create a farm-like environment for the colony.
11-1-3-c: Create three farm animals for the colony.

11-1-4-a: Now create a renewable source of oxygen!
11-1-4-b: Create the primary source of oxygen on earth.
11-1-4-c: Add plant life to the colony.