  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. The point is...the maximum legal weight that an 18-wheeler can weigh is 40 tons (80,000 lbs). If they weighed any more, then they would damage the roads more rapidly than they are even now. But a semi-truck can exceed that limit for certain situations.