I liked the Kim Stanley Robinson method of redirecting comets to impact with Mars. It'd be a lot more interesting way of terraforming then slowly bottling LA air to send to Mars.

Actually, I think his books hit on a lot of good points, esp. the number of people that would react to any sort of human involvment. Keep Space Pure, etc.

And, of course, that you'd need an elixer of youth to properly see terraforming succeed within your life.

The geology of the Tharsis uplift region may indicate geothermal activity of a super volcanic magnma chamber 5-6 miles below the surface. The corresponding volcanic features, Olympus Mon, etc, possibly could have emptied the magnma chamber in a series of eruptions eons ago.
Is it pausible that a super-volcanic feature exist on Mars? If so, is it then pausible that highly compressed gas exists in underground chambers or magnma tubes of volcanic origin? Also, is it then pausible a reservior of water could exist?
If, and only if, an asteroid with high concentrations of iron or heavy metals with a diameter of 1.5 miles were to impact the Tharsis region--and thus fracturing the crust to a depth of 7 miles--would release the compressed gas, water--if it does exists at all.
The question being, "Why do humans have the need to transport the gas to Mars, when Mars may have the resources for terraforming the atmosphere already available?"
If the scientific analysis conclude the possiblity of a super-volcano and magnma chamber with concentrations of methane, ethane, CO2, SO2 in the future then why not import an oil rig and strike a well to start releasing the gas and thus increasing the atmospheric concentration of gases. Pop the Champaign Bottle's cork, and watch Mars fizz! Or divert an asteroid to impact the Tharsis region and watch Mars reawaken from eons of sleep. The scientific gain from knowledge and understanding different processes could benefit all humanity.