Mars is one of the Solar System's four rocky planets. The others are: Mercury, Venus and the Earth. Named after the Roman god of war, Mars is also called the "Red Planet". It is roughly half the size of the Earth. A brownish-red, or rust-colored, dust covers most of Mars' rocky surface.
Mars was very different about four billion years ago. Then, it had flowing water, rivers, lakes and possibly a large ocean. The planet must have had thick clouds and an atmosphere with large volumes of carbon dioxide.
Today, Mars is dry, dusty and very cold. Nearly all its atmosphere has gone. Space scientists now believe that the solar wind "stripped away" or eroded Mar’s atmosphere. This is a stream of charged particles that come from the Sun. The erosion of the planet’s atmosphere probably happened over a very long period. A magnetic field protects the Earth's atmosphere from the solar wind.
Within 11 days, three powerful rockets left the Earth. The first lifted off from Japan. High above the Earth's atmosphere, it launched a space probe. The second blasted off from China. This rocket carried an orbiter, a lander and a rover. The third left the U.S. on July 30. It took a rover into space. This rover carries a miniature helicopter. Each of the space vehicles is now on their way to Mars. All are expected to arrive in about six or seven months.
One Martian year is equal to 687 Earth days, or 1.88 Earth years. Mars rotates, or spins, at a similar speed to the Earth. One day, known as a sol on Mars, lasts for 24 hours and 39 minutes.
Mars and the Earth orbit the Sun at different speeds. There are times when Mars is very far away and times when it is much nearer. The two planets align about once every 26 months. Mars space missions that set off at this time have a far shorter journey. This explains why the three rocket launches were timed within 11 days of each other.
The Japan rocket launch space probe is called Al-Amal. This is Arabic for "Hope". The probe was made and is operated by scientists in the United Arab Emirates (UAE). The country has launched satellites before, but this is its first space, or interplanetary, mission. The UAE paid the Japanese space agency for the rocket launch.
When Hope reaches Mars, it will start to orbit, or circle, the planet. Its orbit will be elliptical. At its closest, Hope will be 20,000 kilometers from the Red Planet. At its outermost point, the probe will be twice as far from Mars. Hope will study Mars' day-to-night cycle. The probe will also record Mars' weather and atmosphere. It is expected to continue to collect this data for one Martian year.
Rovers are remotely operated wheeled-vehicles that can travel over a planet’s or moon’s surface. In the past, China has landed two rovers on the Moon. Last year, it successfully landed on the far side of the Moon. China has never sent a space mission to Mars before. In the past, Russia, India, the U.S., and the ESA (European Space Agency) have all sent probes or orbiters to Mars. However, only America has successfully landed a rover on Mars and completed surface missions.
China's Mars mission is called Tianwen-1. The name means "questions to heaven". When it arrives, the probe will begin to circle Mars. It will release a lander and a rover. The lander is like a small table or platform. The rover sits on top of it. Once the lander is on the surface, tracks extend down to the ground. These allow the rover to drive off the lander and onto the Martian surface. The rover's instruments will investigate and analyze the Martian soil.
Other space scientists describe China’s first Mars mission as "ambitious". China plans to send another mission to Mars in 2030. This would bring Martian rock and soil samples back to the Earth. The Tianwen-1 mission has been planned as a "stepping stone" for China's 2030 objective.
In the past, six landers or rovers have been sent to Mars. The first two were Russian. Both failed. The next four were all American. The third American rover was called Opportunity. It landed in 2004. Two years ago, an unusual dust storm appeared on Mars. It engulfed the whole planet. The storm “knocked out” Opportunity and all communications were lost.
America’s Curiosity rover touched down on Mars eight years ago. A six-wheeled vehicle, it has been very successful. Curiosity is equipped with cameras, a microscope, and a laser-firing instrument. The rover has traveled over 20 kilometers. It continues to move about on the Martian landscape.
The U.S.’s latest rover is called Perseverance. It is an updated version of Curiosity. Perseverance’s landing site looks like a dried-up river delta. The rover will drill deep beneath the surface to search for water and possible microbial life.
Perseverance is carrying a small helicopter. Named Ingenuity, it is a test vehicle. The scientists working on the mission want to find out if it is possible to fly on Mars. The planet’s atmosphere is 99% less dense than the Earth’s. To take off, Ingenuity’s blades have to spin much faster than a helicopter on the Earth. If it does manage to rise above the ground, it will be the first-ever powered flight on another planet.
