much larger than on Earth, typically around 70 °C (125 °F). However, the day/night temperature variation is much lower during dust storms when very little light gets through to the surface even during the day, and instead warms the middle atmosphere. Water and climate Water on Mars is scarce, with rovers Spirit and Opportunity finding less than there is in Earth's driest desert. The climate is much colder than Earth, with mean surface temperatures between (depending on the season and latitude). The lowest temperature ever recorded on Earth was 184 K (−89.2 °C, −128.6 °F) in Antarctica. Because Mars is about 52% farther from the Sun, the amount of solar energy entering its upper atmosphere per unit area (the solar constant) is only around 43.3% of what reaches the Earth's upper atmosphere. However, due to the much thinner atmosphere, a higher fraction of the solar energy reaches the surface as radiation. The maximum solar irradiance on Mars is about 590 W/m2 compared to about 1000 W/m2 at the Earth's surface; optimal conditions on the Martian equator can be compared to those on Devon Island in the Canadian Arctic in June. Mars' orbit is more eccentric than Earth's, increasing temperature and solar constant variations over the course of the Martian year. Mars has no rain and virtually no clouds, so although cold, it is permanently sunny (apart from during dust storms). This means solar panels can always operate at maximum efficiency on dust-free days. Global dust storms are common throughout the year and can cover the entire planet for weeks, blocking sunlight from reaching the surface. This has been observed to cause temperature drops of 4 °C (7 °F) for several months after the storm. In contrast, the only comparable events on Earth are infrequent large volcanic eruptions such as the Krakatoa event which threw large amounts of ash into the atmosphere in 1883, causing a global temperature drop of around 1 °C (2 °F). These dust storms would affect electricity production from solar panels for long periods, and interfere with communications with Earth. Temperature and seasons Mars has an axial tilt of 25.19°, similar to Earth's 23.44°. As a result, Mars has seasons much like Earth, though on average they last nearly twice as long because the Martian year is about 1.88 Earth years. Mars' temperature regime is more similar to Earth's than all other planets‘ in the solar system.