1) Seasonal frost accumulates behind boulders on Mars and shields the area from sunlight. As the sun rises higher in the sky, the temperature behind boulders rises rapidly, such as increasing by 100K within a sol. 2) While the melting point of water is reached, evaporative cooling prevents the formation of liquid water. Instead, briny solutions can form in favorable conditions with high energy input and where salts are present in the substrate. 3) For liquid water to exist, the atmospheric pressure would need to be much higher than the current levels on Mars to reduce evaporative cooling effects. Overall, the model shows that pure liquid water is not stable on the surface of Mars today, but br