Abundant deuterium is taken as clear evidence that Venus once had 150 times as much water in its atmosphere as today, he said. This is because the water's ordinary hydrogen has escaped. This means that much more hydrogen had to escape to build up the present high deuterium concentration. They are the same as the radio signals used in most lightning studies on Earth. Here also, the magnetic fields which channel the signals were the strongest ever seen on Venus' night side.
Some scientists continue to doubt Venus lightning.
They say only optical sightings can prove lightning. A Russian spacecraft has reported visible-light sightings of lightning. Four Russian spacecraft and the U.S. Galileo craft also have observed radio signals believed from lightning. The ionosphere was much different between solar maximum and minimum, which are high and low periods of storm activity on the sun and in the solar wind. At minimum, it was far smaller.