The late planetary scientist and astronomer Dr. Tom Gehrels, (left in 1974 and right in 2011)
My mind has felt like a bowl of intergalactic soup since last night when I chanced upon a piece in Discovery on NASA’s Voyager mission. Although he was not directly connected with the Voyager mission, one name that kept bubbling up that soup was that of the late distinguished planetary scientist and astronomer Dr. Tom Gehrels.
My reminiscence about Dr. Gehrels specifically took me back to 1978 (or was it 1979?) when he was visiting my hometown Ahmedabad’s Physical research Laboratory (PRL) where he was a lifetime fellow. I was about 17 (or 18) and, in retrospect, a fully certifiable astronomy nerd. I fixed up an appointment with Dr. Gehrels on a whim after hearing a lecture by him. I remember telling him that I had a few questions about the Pioneer mission, which predated the Voyager mission and on which he had a key role as the Principal Investigator for the Imaging Photoplarimeter. Of course, I did not know any of this when I sought a meeting with him. For me the the trigger was a fascinating animation that he showed during his lecture about the Pioneer flybys of Saturn. The actual flyby happened only 1979.
If Dr. Gehrels was amused at the sight of a teenager dressed in a shirt tucked inside a trousers with a pair of neatly polished shoes asking for his time, he did not show it. There was not a hint of condescension in his manners. He asked my brother Manoj, another friend Paresh and I to come to the PRL the next day. Although I had Manoj and Paresh with me, I had arrogated to myself the role of the principal interlocutor with Dr. Gehrels. The journalist in me was evidently born earlier than I had the sense to recognize it.
True to his word, Dr. Gehrels was waiting in his PRL office at the appointed time when we reached looking molested by Ahmedabad’s violent summer heat. The air-conditioning in his office was a source of great comfort. Dr. Gehrels inquired about us and what we studied. You have to bear in mind that this was perhaps for the first time in our lives that all three had to converse in English. I took the lead in answering although Manoj was the only one among us who was studying in a school where the medium of instruction was English.
Conscious that I may run out of my limited knowledge of English, I gave what must have felt like a rather abrupt introduction of our lives. I wanted to get on with my questions and I did. The one that I remember the most had to do with the Saturn flyby. I asked Dr. Gehrels why the Pioneer spacecraft would not travel through Saturn’s rings. Was it because they (NASA) feared a collision with the icy particles in the rings?, I asked. He said that was indeed one of the concerns. Close to three and half decades later I still delude myself that Dr. Gehrels’ face had registered the astounding intelligence of that question. I suspect though that in reality it was an expression of indulgence that someone who knows a lot has towards someone who knows almost nothing. Looking back it is clear to me that I was winging the conversation on a very thin air current, a habit that has continued throughout my career.
The general memory of that meeting is about a noted scientist showing the grace to spare time for three teenagers, one of whom may have come across as somewhat annoying and precocious. I don’t have to tell you who that might be.
The point is that it was Dr. Gehrels’ remarkable graciousness and encouragement during that hour-long meeting that has helped sustain my deep interest in science and physics in general and astronomy in particular all these years. An impulsive Google search last night revealed that Dr. Gehrels passed away on July 11, 2011. Had I bothered to find out about him even early last year I could have revisited him, this time dressed in reasonably hip clothes, fully conversant in English, and engaged him in a far more knowledgeable conversation.
The Pioneer 11 mission, in which he was closely involved, sent its last signal on September 30, 1995.
The Discovery piece that catapulted me towards Dr. Gehrels has some fascinating details about the Voyager mission. Prompted by the article I checked this morning on NASA’a Voyager website and found that Voyager 1, launched in 1977, remains in good health. It is now 18 billion kilometers from Earth (about 12 billion miles) and believed to be in intergalactic space. It has left our planetary system for good and is already encountering charged particles outside our solar system. It takes nearly 17 hours for the data signals from the spacecraft to reach us.
Voyager 2 is about 4 billion kilometers behind its predecessor and together they make the most distant “representatives of humanity” as NASA puts it. You can track the distance traveled by the two in real time here.
So thank you, Dr. Gehrels.