Why United States NASA, China, and UAE are all going to Mars at the same time

NASA just launched its Mars rover Perseverance, perched atop an Atlas V5 rocket. But NASA wasn't alone….In the past two weeks, space agencies from China and the United Arab Emirates also launched missions to Mars. These spacecraft will travel over 400 million kilometers before all reaching their destination around February 2021. But in the past 13 years, only seven rockets sent missions to the red planet. So, why are so many attempts to reach Mars all happening right now?