The astronauts who perished in the doomed shuttle may seem too superhuman to be role models for the rest of us.

Those of us tethered to Earth by our own mediocrity can take heart, though, in one inspiring fact:

All were middle-aged.

“I’ve been marveling all morning that all seven astronauts were in their early to mid-40s,” a friend e-mailed me the day after the tragedy.

“It occurs to me that middle age tends to make us timid — I personally stopped horseback riding because I figured a mom with a head injury or a broken back wasn’t much good to anyone,” she wrote.

“Yet here’s this crew of 40-year-olds traveling at mach 18 1/2, including two perimenopausal women who I imagine were not up in space bitching about ‘senior moments.'”

Doubtful, too, that Laurel Clark and Kalpana Chawla, both 41 — the youngest along with pilot William McCool — worried about whether their space suits were flattering to their expanding waistlines.

Israeli Ilan Ramon was the oldest, at 48.

In some ways, it makes sense that the astronauts would be older: The experience and maturity needed to qualify for the strenuous, dangerous task takes more than a few decades to attain.

But it seems that most of us are more fixated on what we’ve lost in our 40s — hair or skin tone, agility or opportunity, to name a few — to consider the possibilities life still has to offer.

The Columbia crew members were culminating their lifelong ambition, not coddling memories of their youth. They were barreling through space, not debating the efficacy of Botox.

Clearly, the boundaries of youth have been pushed back by the flank of baby boomers who’ve redefined midlife.

Dr. Gene Cohen, for instance, points out the difference between now, when all the Columbia astronauts were above 40, and the 1960s, when space flight was in its infancy.

“When John Glenn made his first flight, he was the oldest at 40, and there was question at that time as to whether he was too old — just to show how things have changed,” said Cohen, director of the Center on Aging Health and Humanities at George Washington University.

“Our understanding has changed about fitness, how long one can be fit.”

Glenn, of course, went back into space when he was 76.

Fit or not, midlife is exactly that: the halfway mark that tends to bring a sobering recognition of time lapsed and time left.

These seven men and women on the Columbia deeply understood the repercussions of risk, more than younger souls who might be shielded by the illusion of invulnerability.

And still, they were willing to chase the dream, to soar along an upward arc rather than concede to limits.

There’s a lesson to be learned in that, even if the astronauts who perished may seem too superhuman to be role models for the rest of us.

“I am reminded,” my friend wrote in her e-mail, “to reach higher and take more chances.”

— Jill Porter is a columnist for the Philadelphia Daily News. Her e-mail address is porterj@phillynews.com.