If small comets are as numerous in the inner solar system as Frank et. al. [1986a> have recently proposed, large and easily detectable amounts of hydrogen would be generated in interplanetary space. Inhibition of water vapor production by a factor of 3¿10-9 by very thick dust mantles would be necessary to prevent excitation of a detectable interplanetary Lyman &agr; glow. Other optical problems associated with the cometesimals are also discussed. ¿ American Geophysical Union 1987