original: The rotation period could not be estimated conclusively (best fit ~ 4 h).
simplifications: The rotation period could not be estimated for certain. The rotation period can't be calculated exactly. The rotation period could not be reliably measured. (best fit - 4 h) The rotation period could not be estimated without doubt. The rotation period could not be estimated (best fit ~ 4 h). The rotation time could not be estimated for sure (best fit ~ 4 h). The time of rotation varies. It is usually about four hours. The rotation period could not be decisively guessed. The rotation period could not be certainly estimated (best fit ~ 4 h). The rotation period could not be definitely estimated (best fit ~ 4 h).