According to the 7/30/2012 NASA article William Shatner and Wil Wheaton narrate new NASA Mars Curiosity Rover video, "The video will be used at events around the country and shared on the web and social media. The goal is to educate the public about Curiosity and build awareness about the landing at 1:31 a.m. EDT, Aug. 6."
Curiosity, also called the Mars Science Laboratory or MSL, was launched on November 26, 2011 for its trip to Mars. It is scheduled to land in the Gale Crater at about 05:31 Greenwich Mean Time (GMT), or 1:13 a.m. Eastern Daylight Time (EDT), on August 6, 2012. The rover's objectives include determining Mars' habitability, studying the Martian climate, analyzing the Martian geology, and collecting data for future manned missions to Mars.
Now, in August 2012, the spacecraft, is poised to set its wheels onto the Martian surface. However, the trip to reach the surface of Mars is one of the most dangerous to be attempted on another celestial body.
Curiosity will decrease its speed from 13,000 miles per hour (21,000 kilometers per hour) to 0 mph (0 km/hr) in only 7 minutes. Consequently, this time sequence has been dubbed the "seven minutes of terror."
Go to the following NASA site to see the Shatner video: http://go.nasa.gov/N7eV2N
The second video is called "Will Wheaton and the Grand Entrance" It is also captioned as, "As NASA prepares for Curiosity rover landing on Mars, Wil Wheaton shares this thrilling story of NASA's hardest planetary science mission to date. The video titled, "Grand Entrance," guides viewers from entry through descent, and after landing."
Go to the following NASA site to see the Wheaton video: http://go.nasa.gov/N7f8D8
Both videos look strangely similar, probably because they are the same, except for whom (Shatner or Wheaton) is doing the narration.
The YouTube video "Wil Wheaton and the Grand Entrance" -- as seen above -- has the following caption: "Actor Wil Wheaton talks about NASA's Mars Science Lab mission that will land August 6 2012. more about the mission http://mars.jpl.nasa.gov/msl/"