Seriously? Everyone making that argument is ALSO going to die (albeit not on the way to, or on, Mars) and some of them are likely to die even sooner than the Mars crews (if they actually take off) from any of the many causes of mortality right here. People die. It's what we do. It is, besides being born, the most comprehensive and universal thing people do. We all die. We don't all eat any particular food. We don't all have sex. We don't all speak any particular language. We don't all have sight (some are born blind) or hearing (ditto) or like/dislike/believe/disbelieve/ any particular thing, but we're all born (with or without medical assistance) and we all die (with or without medical assistance.).
So fretting that people who choose to go on an expedition they know is dangerous are going to die...is silly, and also presumptuous. Humans have been dying for tens of thousands of years. The ones who stayed home died. The ones who migrated died. The ones who went out and did dangerous things, new things, died in droves. The ones who fought in wars and the civilians in whose lands war raged died. Every time someone set to sea in a boat, or went down a mine to return with some treasured mineral, or went up in the air in a balloon, kite, dirigible, aircraft...the possibility of death rode their shoulders, and many times the reality of death came to them. People die of their own carelessness, their own ignorance, their own refusal to think ahead...but the prudent who may live somewhat longer will did in the end, of something else. Nothing--not a "healthy diet," not the right supplements, not "staying fit", not excellent medical care, not "healthy genes"--will keep someone alive forever, though it may (only may) make one's lifespan more pleasant longer.
I am alive as I write this, a few weeks from being 70, and my death may be less than a minute away (if I have a catastrophic stroke, a heart attack, or the house blows up--we use propane for heating--or an angry person barges in and blows my head off. Or it may be thirty years (with one parent who lived to almost 102, that's a possibility) or more, or any point in between. Today, tomorrow, the day after, next week, next month, next year, next decade...or two... In one or another scenario (the kind novelists can think up easily) I might die of suffocation, of poison gas, of drowning, of deliberate attack by individuals or groups, of unintentional (but effective) carelessness or incompetence of an individual or group, of the incidental breakdown of technology designed and maintained by fallible humans, of infectious disease, of non-infectious disease like cancer or auto-immune disease, of attack by an animal or unintentional injury by an animal. Like many of us, I have thought about how I'd like to die...but I know (six years as an EMS volunteer in a rural area taught me) that this is a wish, not a reality.
I will continue to put myself in situations in which such deaths are slightly more likely (driving a car on a crowded highway, riding on public transportation, riding my bike on streets shared with cars and trucks, disagreeing with people who may turn violent, joining others to protest policies I think wrongheaded, quite possibly riding horses at speed again (I hope), trying new foods (to which I might, though unlikely, be allergic), because a) that's what life is, and b) I know that no amount of being careful will keep me alive forever. I know my death is inevitable, and I'm a lot closer to it now than I was at birth. And that's the way it is: it's like gravity, just there. When I fall and hit the ground and it hurts, I can wish gravity didn't have that effect (not a fan of broken ribs, personally), but it does have that effect and wishing doesn't change it. Death is in my future. I feel no desire to "rage" about that. I feel a desire to knit more socks, cook more meals, walk the land as long as I can, sing more great music, write more stories, love friends and family, do stuff, keep on being alive until...I'm not.
So: assuming the people planning on that trip to Mars weren't shanghaied off the street corner, snatched from their own homes...yes, they will die, but they will die in no worse case than many others in human history. They are no crazier than the people who went on one or another exploratory voyage, the ones who left a familiar place to go try to find a better one, the ones who experimented with electricity or steam power, or internal combustion engines.
(EDITED today, February 19) Note: All "Anonymous" posts go to moderation. if you are not a LJ member and post anonymously, you should identify yourself in some reasonable way in your comment ("Hi, I'm J. Brown from Iowa, a soybean farmer. I've read your LJ before and this is the first time I've posted..." or "I'm Mary S, I post as @[some interesting moniker] on Twitter and this is my first time here") before the comment. Otherwise, you may sit in moderation a LONG time as the moderator ponders whether this is a can of worms best left untouched, and gets on with the moderator's other work. Posting as "Anonymous" without introducing yourself at all is like wearing a ski mask when you walk into someone's house...there's a certain suspicion about people who aren't willing to disclose their identity.