No, it is not.

It used to have a thick atmosphere, perhaps thicker than Earth’s. It had that atmosphere for a couple of billion years and had oceans. It looked about like this.

The issue is it lost its magnetic field because it doesn’t have a large moon to stir its core with tidal forces. The core is molten iron even today. The magnetic field blocks the solar winds. Once it was gone the solar winds slowly stripped off the atmosphere over tens of millions of years, Mars got cold, and all of that water froze in place.

There are a couple of ways a planet can lose atmosphere. The one associated with size is called Jean’s loss. It is simple kinetic loss where the kinetic energy of some molecules in the extreme upper atmosphere exceed the planet’s escape velocity. Those extreme outliers are lost to space. Note that their velocity is a function of temperature and molecular mass, with low mass equaling higher velocity and therefore more likely to escape. This plot shows the relationship.

Notice that Mars is in the same band as Earth. That says that due to its lower upper atmosphere temperature it is just as able to hold in an atmosphere as Earth, and it once did. It just needs a magnetic field to not slowly lose one due to solar winds.