It’s only a problem if they aren’t earthlife, or something close enough to earthlife to suggest that somewhere else in the solar system was the common home of earthlife and marslife.

The earth has seeded every body in the solar system with biologically active rocks for billions of years; just as there are martian meteorites on Earth, there are earthian meteorites on Mars (and every moon of Jupiter and Saturn, etc.)

It’s likely there is life all throughout our solar system. And it is likely all that life has some common, nearby ancestral home. Occam’s Razor suggests that home is Earth.

The best data we have suggests that life appeared on earth unreasonably early after its reformation following being whacked by a planetary neighbor. A minimum, there is life on earth 3.77 billion years ago, and that number keeps being pushed back further and further with some research suggesting that life appeared over 4 billion years ago. Either it spontaneously occurred on Earth or it came to Earth from somewhere else early in the formation of the solar system — either way, asteroid and comet impacts with Earth have been spewing earthlife all over the solar system for billions of years.