In Seveneves by Neal Stephenson, a breakaway group launches a Mars mission. A preliminary mission is sent but is it ever revealed what happened to it?
Short version: The text doesn't positively indicate anything one way or the other, but states that they are believed to have perished:
As for the tiny faction that had split away on Red Hope, it was assumed that they had long since been wiped out by one or more of the hazards and calamities that had inflicted such a death toll on the Swarm.
(spoilers throughout, not individually protected)
Supporting the above quote, there are at least three reasons to infer that they perished:
- The daunting technical barriers to survival, such as their increased vulnerability to radiation once en route to Mars, and their limited resources.
- The astonishingly poor survival rate of the Cloud Ark brethren, who were using the same equipment and had more resources, that they left orbiting Earth.
- Zero mention of Mars, or Martian descendants, is made in the "Five Thousand Years Later" portion of the book, especially when much is being made of meeting other surviving sub-races (the Diggers and the Pingers).
Even more speculatively, it is hard to imagine that the Red Hope mission could have reached Mars and survived without enough technology to communicate with the ISS or the Swarm. As Sean Probst's example with they Ymir mission showed, even a primitive spark gap transmitter is possible with limited resources. If Red Hope made it to Mars, and had enough resources to sustain life in that adverse environment, then they'd have had enough resources to telegraph "Hey, we made it!"
Just to clarify the various parties -
The Red Hope mission, consisting of a heptad, a triad, and a propulsion MIV, was not heard from after the Break (in the book; if they were heard from in the story universe, it was never mentioned in the book).
Julia called for the AC ("Arkie Community") to follow her away from the ISS and into a higher orbit at the same time that Red Hope left, triggering the Break:
The open vista of clean space beckons above us. Red Hope will soon fire its main engine and begin its trek across that unexplored frontier to a planet that will one day have room for us all. The Cloud Ark cannot follow her - yet.... [my friends and I] will initiate a burn of our main propulsion that will lift us clear of the drifting debris... and move us in the direction of clean space. Our orbital parameters will be posted openly on the network so that like-minded members of the AC may join us...
At the end of the day of the Break,
surviving, occupied arklets... had been reduced to 282 by the collision. Ten of them - a heptad and a triad - were attached to Red Hope, leaving 272. Approximately 200 were missing and presumed to have flown the coop with [Julia]. The remaining 70 or so had elected to stay behind and were still reporting in as members in good standing of the Cloud Ark.
Those of the AC who left for higher orbit are referred to as "The Swarm." At the time of the Break,
The population of [Julia]'s breakaway swarm must have been something like 800 souls. She had taken two-thirds of the human race with her.
When they get back in touch 3 years later, the Swarm is
"How many do you have?" Doob asked.
A thought came to him. "Do you mean eleven arklets?" That would imply scores, or maybe a hundred people.
Aida looked amused. "Oh no, of arklets we have many more. We have twenty-six."
"Ah. So what is it you have 11 of?"
"People," Aida said.
If the Swarm went from 800 to 11 people, then the 24 people on the more-dangerous Red Hope expedition probably didn't fare so well.