The Last Aquarius by Eve Langlais

Can this Zodiac Warrior make the ultimate sacrifice?

A prophecy sets Aquarius on an impossible quest. Find a way to reach Mars and convince its queen to help against an alien threat. However, Ishtar, the last Martian Queen, refuses to reveal the secret to destroying the body-snatching invader.

Ishtar still suffers with the guilt of destroying her home world and won’t allow the same thing to happen to Earth.
How is Aquarius supposed to convince her? His boss says to lather on the charm. However, this warrior geek is better with computers than women.
What if he could give her the one thing she longs for? And no, he’s not talking about the most epic time in bed—although he gives it his best shot.
Surely there’s a way to rid Earth of the alien threat without turning it into a dusty wasteland like Mars. The problem is the prophecy seems pretty clear. To succeed, the water-bearing Zodiac will have to sacrifice his life.

So be it. A final noble act to save the world—and the woman he loves.