The real question is, **Why would they risk Watney's life for another two years? ...when they've already chosen option (b).**

**Option (a):** send the probe on a *fly-by trajectory* towards Mars, use aerobraking and what little fuel it has to be captured, and eventually impact the surface without **1)** destroying its cargo, and **2)** landing more than *60 km* away from Watney's position, and hope that Mark can survive another *two years* without **3)** another airlock tearing open, **4)** his *water-reclaimer* breaking (= dead), **5)** his *oxygenator* breaking (= dead), **6)** his *hab*, designed for a 31-day mission and already greatly overused, ripping open in some *other* location besides the airlocks (= most likely dead), and finally **7)** Mark losing sanity from isolation for 2 additional years. 

>! Remember at this point, Mark has accidentally fried Pathfinder so he once again has no way to talk to NASA. He modified the drill he was using to cut holes in the rover from using *batteries* to running off *hab power* from a cable, and leaned it up against Pathfinder with exposed wires... *oops*. Hab power has 6 amps, Pathfinder was only built for 0.6 amps. At this point, he *had* to get to the Ares IV MAV just to make contact again. In the book, Mark's great sense of humor is what keeps him sane most of the time, but *two years* is a serious test on anyone's sanity.

**Option (b):** send the Hermes on a *fly-by trajectory* to Earth for gravity assist to a *fly-by trajectory* to Mars, hoping that **1)** the resupply from the *Taiyang Shen* is successful, **2)** Mark can modify the MAV to be light enough to reach Mars' *escape velocity* and rendezvous with the Hermes, and **3)** the Hermes can survive deep space for another 2 years past its maintenance window.

So essentially, you question is *"why, when the Hermes was already on its way to Mars, did it not just drop off the care package and leave Mark for another 2 years?"* *"This would've been safer for Watney and would've saved the Ares IV MAV"*

Let's call this **option (c)**, and you will see very soon here that all we're doing is stacking the ***worst risks*** from both options (High probability of killing 1 person vs. low probability of killing 6 people) with the *only* real payoff being: ***We get to keep the Ares IV MAV.*** 

**Option (c):**  send the Hermes on a *fly-by trajectory* to Earth for gravity assist to a *fly-by trajectory* to Mars, hoping that **b-1)** the resupply from the *Taiyang Shen* is successful,  **b-3)** the Hermes can survive deep space for another 2 years past its maintenance window, release the probe on approach at *escape velocity* towards Mars, use aerobraking and what little fuel it has to be captured, and eventually impact the surface without **a-1)** destroying its cargo, and **a-2)** landing more than *60 km* away from Watney's position, and hope that Mark can survive another *two years* without **a-3)** another airlock tearing open, **a-4)** his *water-reclaimer* breaking (= dead), **a-5)** his *oxygenator* breaking (= dead), **a-6)** his *hab*, designed for a 31-day mission and already greatly overused, ripping open in some *other* location besides the airlocks (= most likely dead), and finally **a-7)** Mark losing sanity from isolation for 2 additional years.