In The Lion of Mars, Holm explores two major themes, isolation and The Importance of Community, to highlight the importance of communication and cooperation. The novel’s setting is especially ripe for depicting both physical and social isolation, as the settlers are physically distant from Earth and disconnected from other people. Living on Mars also creates a sense of alienation from the reader’s standpoint, which contrasts with Bell’s own perspective. At first, Bell does not feel isolated because he has no other frame of reference. However, he eventually comes to realize how alone the American settlers really are once he experiences social connection and life beyond the settlement.

A lot of real, physical dangers that can befall Mars settlers are caused by isolation: They might run out of supplies, break mechanical parts, face natural disasters, or get injured. When the adults get sick and the children message Earth command for help, Bell realizes the truth about their situation:

Command always responded the same way: we’ll send whatever you need on the next supply ship. At first, it struck me as a little cold, but then I realized it was all they could do.