Rotating GameObject does not rotate child

I am rotating a gameobject that has a child game object with a particle effect on it.

It's a missile with engine exhaust.

I am rotating the parent game object but the particle effect child objects do not rotate:

The missile object has this script on it:

void FixedUpdate () {
Vector3 dir = targetObject.position - transform.position;
dir.Normalize();

float zAngle = Mathf.Atan2( dir.y, dir.x ) * Mathf.Rad2Deg - 90;
Quaternion desiredRotation = Quaternion.Euler( 0, 0, zAngle );

transform.rotation = Quaternion.RotateTowards( transform.rotation, desiredRotation, 10.0f * Time.deltaTime );
rigidBody.AddForce( transform.up * 10.0f, ForceMode2D.Force );
}

Particle Effect:

Anyone see what I am doing wrong?