Um.

SIDS isn't a mystery as such, its just not always possible to pinpoint the exact reason the infant died.

SIDS is often down to dangerous sleeping habits, for example :

1. Sharing a bed with a parent
2. Overheating when sharing a bed
3. Parent falling asleep with babe in arms on the sofa or armchair
4. Parents/guardians being smokers/drug users.
5. Being accidentally smothered with loose blankets.

Small children, particularly infants, are very fragile life forms.

Because half the time those mummies have a damn axe hole in their skulls :-P

Why do we know more about space than our oceans ?

Idk bro but what I do know is nothing ever really is 'unexplainable' as such. Not until the facts of the matter come out anyway... So maybe they're yet to fully identify and/or disclose all the notable possibilities that could've led up to the deaths