Nasa's Perseverance rover sent a cheerful message to the Hope probe to congratulate it on a successful launch on Monday.
"Congratulations on your launch!" Nasa wrote on Twitter.
"I wish you a successful journey and look forward to the sol [Martian day] when we are both exploring Mars."
Hope's team responded: "Thank you. The launch was really exciting. I wish you all the best for your big day. See you soon!"
Nasa is working to a similar launch window to send Perseverance to the Red Planet.
It was due to blast off from Cape Canaveral, Florida, on July 17 but the launch has been scrubbed three times due to technical problems.
Engineers have until mid-August to make the launch window, after which the distance between Earth and Mars would be too great to travel.
If the launch goes ahead, Perseverance is due to land on Mars' surface in February 2021 to search out signs of past microbial life - if that ever existed.
It would be the first mission to specifically hunt for so-called biosignatures since the twin Viking 1 and 2 launches in 1975.
The two landers successfully reached Mars and were the first to send home images of the surface of the Red Planet.
Both operated far beyond their 90-day lifetimes, to 1980 and 1982 respectively, offering scientists an unrivalled insight into Mars.
A third Mars mission is planned for this month when China attempts to send its Tianwen-1 vehicle to Mars.
It aims to complete orbiting, landing and roving all in one mission and is equipped with a range of devices to measure minerals and particles.
It is due to land on a region of Mars called Utopia Planitia, where Viking 2 touched down in 1976.
If Nasa and China's missions cannot take off during the launch period, they would have to wait until 2022 when Earth and Mars align again.