  Earth's atmosphere, on the other hand, is mostly nitrogen (78%) and oxygen (21%) with 1% being a mix of hydrogen, carbon dioxide and others. So you can see that Mars has much less atmosphere than the Earth does and oxygen make a proportionally much smaller fraction of of what there is than what we have on Earth.
Pickup trucks come in different shapes and sizes, and their weight entirely depends on the make and model. On average, a common pickup truck can weigh up to 3 tons, equivalent to 6,000 pounds.
The semi-truck without the trailer weighs around 20,000 lbs. An empty trailer weighs around 12,000 lbs, but it depends on what type of trailer it is. There are hundreds of different configurations.