One of the symbols of Rome is the Colosseum (70–80 AD), the largest amphitheatre ever built in the Roman Empire. Originally capable of seating 60,000 spectators, it was used for gladiatorial combat. A list of important monuments and sites of ancient Rome includes the Roman Forum, the Domus Aurea, the Pantheon, Trajan’s Column, Trajan’s Market, the Catacombs, the Circus Maximus, the Baths of Caracalla, Castel Sant’Angelo, theMausoleum of Augustus, the Ara Pacis, the Arch of Constantine, the Pyramid of Cestius, and the Bocca della Verità
In the winter of 1994 the European Space Agency’s Mars Express found an ultraviolet glow coming from “magnetic umbrellas” in the southern hemisphere. Mars does not have a global magnetic field which guides charged particles entering the atmosphere. Mars has multiple umbrella-shaped magnetic fields mainly in the southern hemisphere, which are remnants of a global field that decayed billions of years ago.
In late December 2014, NASA’s MAVEN spacecraft detected evidence of widespread auroras in Mars’s northern hemisphere and descended to approximately 20–30 degrees North latitude of Mars’s equator. The particles causing the aurora penetrated into the Martian atmosphere, creating auroras below 100 km above the surface, Earth’s auroras range from 100 km to 500 km above the surface. Magnetic fields in the solar wind drape over Mars, into the atmosphere, and the charged particles follow the solar wind magnetic field lines into the atmosphere, causing aurora’s to occur outside the magnetic umbrellas.
On 18 March 2015, NASA reported the detection of an aurora that is not fully understood and an unexplained dust cloud in the atmosphere of Mars.
Like Earth, Mars has differentiated into a dense metallic core overlaid by less dense materials. Current models of its interior imply a core region about 1,794 ± 65 kilometers (1,115 ± 40 mi) in radius, consisting primarily of iron and nickel with about 16–17% sulfur. This iron(II) sulfide core is thought to be twice as rich in lighter elements than Earth’s core. The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but it now appears to be dormant. Besides silicon and oxygen, the most abundant elements in the Martian crust are iron,magnesium, aluminum, calcium, and potassium. The average thickness of the planet’s crust is about 50 km (31 mi), with a maximum thickness of 125 km (78 mi). Earth’s crust, averaging 40 km (25 mi), is only one third as thick as Mars’s crust, relative to the sizes of the two planets. The InSight lander planned for 2016 will use a seismometer to better constrain the models of the interior.
Sojourner was the Mars Pathfinder robotic Mars rover that landed on July 4, 1997 and explored Mars for around three months. It has front and rear cameras and hardware to conduct several scientific experiments. Designed for a mission lasting 7 sols, with possible extension to 30 sols, it in fact was active for 83 sols. The base station had its last communication session with Earth at 3:23 a.m. Pacific Daylight Time on September 27, 1997. The rover needed the base station to communicate with Earth, despite still functioning at the time communications ended.
Sojourner traveled a distance of just over 100 metres (330 ft) by the time communication was lost. It was instructed to stay stationary until October 5, 1997 (sol 91) and then drive around the lander.