If you mean molecular oxygen, O2, then no, there is no more than trace amounts on Mars (compared to the Earth which has an atmosphere composed of over 20% O2). Our atmosphere is mostly nitrogen (N2) followed by oxygen (O2) with smaller amounts of argon and carbon dioxide.
A ton is 2000 pounds (907.19 kg), so does it follow that a half-ton truck weighs 1000 pounds (453.5 kg)? Actually, the name doesn't refer to the weight of the truck. In fact, half-ton pickups weigh much more than that. The weight of a truck without cargo or passengers is called the curb weight. For example, many 2007 half-ton pickups have curb weights between 9000 (4082.3 kg) and 11000 (4989.5 kg) pounds [source: Edmunds].
In the United States, a short ton is usually known simply as a ton, without distinguishing it from the tonne (1,000 kilograms or 2,204.62262 pounds), known there as the metric ton, or the long ton (2,240 pounds or 1,016.0469088 kilograms), known there as the Imperial ton. Long ton, 2,240 lb (1,016.0469088 kg). 2  Ton. 3  Tonne, also known as a metric ton (t), equal to 1,000 kg (2,204.6226218 lb) or 1 megagram. 4  Tonnage, volume measurement used in maritime shipping, originally based on 100 cubic feet (2.8316846592 m 3).