Although, bear in mind that biological matter on Mars could have been brought from Earth via meteorites.
Even non-discovery of life on Mars is important, and it is instructive to listen to Monica Grady give a talk on this at the Society for Popular Astronomy, especially having to deal with an someone who asks awkward questions (at 01:09:05- people like that have no place in a civilised society, IMHO).
Of course, one question that the discovery, or non-discovery, of life on Mars, raises is the theological one- does it prove/disprove Christianity, or is totally irrelevant?
First, take a step back. I am an evangelical Christian, and have the background of an MSc and a PhD in Astronomy. At no point did I see a clash between Christianity and science. Sadly, there are people who think that Richard Dawkins used science to disprove religion. Similarly, there are Christians who take two interesting views on science- firstly that science and Christianity are bitter enemies, whilst secondly, at the same, time there is something called "true science" which PROVES Christianity (the stage beyond simply proving Christianity).
So, you will get zealous young Christians who will on one hand urge you, if you sincerely love God, to take the step of obedience by withdrawing from a science PhD, while on the other hand shoving magazines in your hand that use science to PROVE a certain interpretation of parts of the Bible. And of course, the proofs show a misunderstanding of basic science.
Alongside that are the supposed little apologetics argument that use "true science" in evangelism. The Sun is shrinking. The Sun is not producing enough neutrinos. The Apollo capsules would have sunk if the Moon were more than a few thousands years old. Scientists PROVED that the decay of comets meant the solar system was a few thousands years old so INVENTED the idea of the Oort Cloud to get an old solar system. The speed of light is decaying- as long as we alter the early results to fit this nice downward curve we've got.
This line of argument often produces the "God-of-the-gaps" as the definitive, knockdown, cannot-be-argued-against proof of Christianity. The problem is that the gaps close up. Even worse is when the "scientists cannot explain X, therefore God" is used for things which were explained ages ago.
I do not lie awake at night worrying that tomorrow some scientist will make The Discovery that brings Christianity crashing to its foundations, and leaves a Cross lying on the ground as meaningless fragments of wood.
Sometimes there will be confusion though. I remember years ago, a new curate (now with the Lord after a battle with cancer) informed she was concerned as she'd been told I was into astrology- someone else had got the two confused. Although one friend likes to get them deliberately confused and is fond of telling me that the best bit of the Old Testament is when the King of Babylon has all the astronomers put to death.
I remember the discovery of what, at the time, were considered to be possible Martian microbes, and recall a statement from one denomination that the Bible teaches that there is no life on other planets. Hmm, where exactly?
So, what are the theological implications of the discovery, or non-discovery, of life on Mars?
One argument given is that the discovery of life would prove that we are not alone, that life appearing spontaneously in two different places would indicate a universe teeming with life. Therefore, there would be nothing special about humanity, and any religion that survived would be Eastern-style with the emphasis on the whole of creation, rather than the religions that arose in the Middle East with their emphasis on humanity.
Leave aside for the moment whether the Eastern religions concentrate on creation and the Middle Eastern ones don't.
There is an interesting question about whether life can appear spontaneously in two or more places. Why do these have to be on different planets? Why not the same planet? Suppose life fairly easily appeared- which would lead to the universe being filled with life. Then surely, we would expect it to have appeared more than once on the Earth, and unless all- except one- of these primitive lifeforms had all their descendants wiped out, then somewhere there would be one lifeform for which we would say "This does not share a common ancestor with anything else". Of course, it is possible that such a lifeform exists and we haven't found it yet.
If no such lifeform exists- and for the moment take a Creator out of the picture and rely on evolutionary theory- then we do not have life appearing all over the place, or if it does, not lasting long and all traces of existence vanishing.
Don't worry at the moment about removing a Creator- I am dealing with the idea that the existence of aliens disproves religions that have a personal Creator.
The fact that there is only one common ancestor on Earth implies that (without a Creator) life is rare in the universe. The existence of life on Mars would strengthen the idea that life is common.
In 1835, the New York Sun ran its famous moon hoax, with the claim that John Herschel had discovered aliens living on the Moon from his observatory at the Cape of Good Hope. Now, what is interesting is the Christian response. There is the urban myth that a missionary society in Missouri looked into sending missionaries to the Moon.
OK, urban myth, but even urban myths tell us something- Christians were not going around panicking that the discovery of selenes was damaging to Christianity. The urban myth is Christians asking how aliens could be evangelised.
What has changed? I think in part, this is Charles Darwin and his theory of evolution. Rather than see aliens as an example of God's creative activity, is there a danger that modern evangelicals see them as a proof of a theory they hold to be anti-Christian?
We should- if alien life, or relics of it, are found- welcome this as another thing that God has created.
By the way, if you want to know what to do if you see a spaceman, my answer is "Park in it, man".