This is the sort of dumbing down that made thermodynamics harder than it had to be. The word ‘heat’ should never be used in the context of thermo, but because it is, it gets confusing - specific heat, etc. ‘Thermal energy’ is the correct term, and once you get into that practice, thermo is easy.
Space radiation is a term not unlike what 18th century scientists used the term ‘ether’ for. ‘The ether’ was a scientific term for a very long time until we got specific about what ‘the ether’ meant.
Bodies emitting thermal energy also emit EM radiation. The sun puts out UV radiation. Hydrogen and helium nuclei emit nutrinos. The Van Allen belts emit radiation. Then there are cosmic rays, which is another ‘ether’ like term, since their sources are myriad. At least cosmic rays are understood to originate outside the solar system.
Most of the radiation occuring on Mars is due to the Sun. As such, they could have designed around it sufficiently, but they apparently didn’t.
I don't believe that they know the 'problem' came from 'space radiation'. They know they have the problem, and are fixing it. All else is speculation. It's not like they have a 'space radiation damage' detector onboard.
“As such, they could have designed around it sufficiently, but they apparently didn’t.”
Single event upsets are difficult to prevent or mitigate. The NASA guys in Greenbelt did years of screening and testing parts, but that will not prevent an SEU, it lets you predict them and try to mitigate with error checking and redundancy. SEU and other single event effects come from particles found in space, usually heavier than helium with a sharp numeric cutoff at iron. The heavier ones carry a lot of LET (linear energy transfer) when they hit your microprocessor.
The big problem is galactic cosmic rays (that’s the official term, often abbr GCR), which are hard to stop and can reach Martian surface. They are heavy and very energetic. The other part of space radiation (short for radiation found in space) is solar electrons and protons (in the solar wind along with small numbers of other particles like iron nuclei), and trapped particles like you find in the van Allen belts.
Yeah the terminology is “wrong” but that’s the language we use in the field.
I don’t think NASA knows what the problem is, but a good guess is radiation, either SEE or accumulated dose.