Hermes
Hermes is the name of the space ship the crew is on coming back from Mars. It is also a Greek god which has been connected to travelers and border crossings as well as a guide to the underworld. All of these references are symbolic in that the Hermes space ship is traveling beyond the borders of space in order to prevent Mark's death.
Video Diary
On Mars, the astronauts use their video diaries to log their daily activities in order to keep track of progress. Mark continues this when he is stranded on Mars and it becomes a symbol of his ability to remain sane as, at the very least, he is able to interact in some way by speaking and recording his thoughts and actions. It symbolizes he is still on course for survival.
Biomonitor
Mark's biomonitor has gone down after he's been struck by debris in the storm on Mars. Because of this he is left behind by his crew as they have no reason to believe he is still alive. This is a symbol that technology, for all of its benefits and greatness, still is not the greatest determiner of life. Survival still requires coordination with humanity.
Out-dated Tech
Mark finds the Pathfinder probe which wasn't used since 1997 in order to create a connection to communicate with Earth. This is a symbol that though we have technologically advanced in our ability to communicate, we were able to do so because of the simpler methods which were tried and utilized in the past. Thus, the importance for understanding the past and the evolution of our society and us within it over time.
Taiyang Shen
This is the classified booster rocket that the Chinese have been developing in secret. When the Chinese scientists lend it to the United States to save Mark, it becomes a symbol that life, since humanity is far more valuable than one nation ruling over another.
