Also, year-round dust storms on Mars may block sunlight for weeks at a time.[25][26] Mars's orbit is more eccentric than Earth's, increasing temperature and solar constant variations. Due to the lack of a magnetosphere, solar particle events and cosmic rays can easily reach the Martian surface.[27][28][29] The atmospheric pressure on Mars is far below the Armstrong limit at which people can survive without pressure suits. Since terraforming cannot be expected as a near-term solution, habitable structures on Mars would need to be constructed with pressure vessels similar to spacecraft, capable of containing a pressure between 30 and 100 kPa.