Why are so many nations going to Mars this summer?
Mars has always been a hypothetical second home for humans.
Scientists expect that plans to send people and colonize the red planet could start as soon as the next decade. But would people really have what it takes to get to and live on Mars?
The first challenge is getting through the launch.
This summer has witnessed 3 spacecrafts heading to Mars.
On July 19, the United Arab Emirates made its first bid to join the Mars game, launching the Amal Probe , or "Hope," spacecraft on a mission to orbit Mars for at least two years while studying its atmosphere.
Four days later, on 23 July, China launched its Tianwen-1 spacecraft to Heaven. It’s a three-part ship with an orbiter, a lander and a six-wheel rover, aiming to complete orbiting, landing and roving in one mission. The probe blasted off on China's largest carrier rocket , the Long March 5, from the Wenchang Space Launch Centre in the southern island province of Hainan. It is expected to reach Mars in February where it will attempt to deploy a rover to explore the planet for 90 days.
On July30, NASA's Mars rover Perseverance has been launched atop an Atlas 5 rocket from Florida on a mission to search for traces of potential past life on Earth's planetary neighbor.
So why all the interest in Mars this summer?
The timing issue has everything to do with planetary mechanics.
As they fly their differing solar orbits with Earth on the inner track and Mars on the outer, the distance between the two worlds is forever changing.
At their greatest remove, when they are on opposite sides of the sun, they are up to 400 million km apart. But once every two years, they line up on the same side of the sun, with just 5.6 million km separating them.
Launches to Mars are targeted at this time because any spacecraft leaving Earth will experience a shorter trip to Mars -- which means less resources such as fuel are needed as well.
Such an alignment is taking place this summer, dramatically slashing inter planetary travel time to the current seven-month itinerary.
So that explains the when question.
Then why is it so hard to land on Mars?
When it comes to landing spacecraft on planets or moons, there's a lower success rate landing on Mars than on Venus, the moon, the earth even Saturn's moon Titan.
This is because Mars's atmosphere is in the perfect goldilocks zone of being a total headache. On the moon(or an asteroid) you can use lightweight spacecraft made essentially out of tinfoil because there's no air to cause drag or pressure or heat.
On earth, or Venus, or Titan, there's enough air that you can land largely unpowered, So you use a lot of weight for heat shields and walls and parachutes, but don't need big rockets or lots of fuel to land.
However, the air on Mars is thick enough that you actually have to deal with it with heat shields and walls, but thin enough that it doesn't help you slow down much and you also need to use rockets.
1. hypothetical adj. 假设的；爱猜想的
2. colonize v. 开拓殖民地
3. rover n. 漫游者；流浪者；巡视器
4. blast off 点火起飞；发射升空
5. planetary mechanics 行星力学
6. alignment n. 队列；成直线
7. itinerary n. 旅程；路线