Theory:

The lesson "An Alien Hand" is written by Jayant Narlikar. The story is about Tilloo, who lived beneath the surface of a planet with his parents. Tilloo's father goes to work through a forbidden passage. Tilloo was restricted to use the path, and he was curious to know why he was not allowed to use it.
 
One day, Tilloo took his father's security card and entered the passage. Before he could move further, a security staff stopped him and escorted him back home. Later Tilloo's father explained to him about the conditions of the surface where he used to work. He told Tilloo that he wore a special suit and an oxygen reservoir to survive on the planet's surface.
 
Then the next day, when Tilloo's father went to work, he learnt that two spacecraft were approaching them. Then the President asked the opinions of his colleagues on how to deal with the situation. Later the President got a phone call, and it was mentioned that the spacecraft had landed on Mars.
 
Later, Tilloo's father brought Tilloo to the Control Room, where he saw the alien spacecraft on the TV screen. Suddenly Tilloo noticed a mechanical hand emerged from the spacecraft, and the excited Tilloo pressed the red button from the control panel. As a result, the robotic hand stopped functioning. In addition, on Earth, NASA's technicians managed to get the mechanical hand functioning. Moreover, the mechanical hand started working and took the soil samples from the Martian surface. At last, scientists studied and concluded that there is no existence of life on Mars.