“One Small Step Back in Time,” by Clara Moskowitz, includes a picture of the firing room for Apollo 11's launch in 1969. I found, amid a sea of crew cuts, white shirts and dark ties, NASA engineer JoAnn Morgan seated at her console. Against the far wall, I could make out three other women. I, and undoubtedly other readers, would like to know more about the women in the control room that day—who they were and why they were there.

ISAAC FREUND Department of Physics, Bar-Ilan University, Israel

MORGAN REPLIES: I cannot identify the women against the wall. They came in the back door to hear the VIP speeches, which occurred 40 minutes or longer after launch. I did not know them, and they could have been clerical staff, procedure or mail-delivery distribution employees, or any variety of administrative contractors in the building.

There were very few NASA women at the facility. In tests, Judy Kersey, the first female guidance systems engineer, would come in to brief her division chief, who sat in my row. But I think she may have been in the Central Instrumentation Facility during the Apollo 11 launch. Note that the firing room doors are unlocked within 30 minutes after launch and once the engine burns of the first and second stages are successful. I also remember Boeing had a woman writer who helped its engineers with procedures.


For the second time in three months, Scientific American has published an item promoting the promise of a revival in nuclear energy. In “Reactor Redo” [May 2019], Rod McCullum describes current research on “safer and more efficient” reactor designs. In “I've Come Around on Nuclear Power” [Ventures], Wade Roush shares how his fear of global warming converted him to support “the nuclear industry's rebirth in the U.S.” Both articles ignore some long-term, practical shortcomings of nuclear power: First, the failure to develop reliable technology and policy regarding spent nuclear fuel. And second, the ongoing cost of nuclear plants once they stop generating electricity.

Nuclear plants may not generate carbon dioxide, but they certainly produce radioactive waste. Regardless of how fuel is initially processed or actually used within a reactor, the radioactive properties of spent nuclear fuel remain fundamentally hazardous. If we feel carbon dioxide is dangerous, let's consider the consequences of a growing worldwide cache of spent uranium.

Roush claims that if the social cost of carbon were properly considered, nuclear power would become more economical than fossil-fuel plants. Besides promoting the false dichotomy of fossil fuels versus nuclear energy, he ignores the substantial cost of nuclear plants even after their utility has passed. Consider how the citizens of California will be charged billions of dollars for decommissioning the San Onofre and Diablo Canyon nuclear plants. Consider as well the costs of Chernobyl and Fukushima.

It is no mystery why the nuclear power industry has been in decline: it is ultimately dirty and inherently dangerous, and it meets its exorbitant costs with a blank check from taxpayers.

GARY D. LAVER Los Osos, Calif.

Having had responsibility for the licensing of several nuclear plants, I agree with Roush that we have far more to fear from climate change than nuclear power. Its continued use makes sense and should be part of the solution, so long as it pencils out.

But Roush is wrong that carbon tax is a “political nonstarter.” As of early September, the Energy Innovation and Carbon Dividend Act (H.R. 763) pending in the U.S. House of Representatives already had 62 House members signed on. It is a revenue-neutral, free-market approach that would impose an effective accelerant to the transition to clean energy.

DOUG NICHOLS via e-mail


“Origin Story,” by Simon J. Lock and Sarah T. Stewart, asserts that Earth's moon was formed from a doughnut-shaped mass of rock vapor—a synestia—after a collision with a Mars-sized body.

The Fermi paradox asks why we haven't detected technologically capable extraterrestrials yet. There are many suggested answers, but among the least far-fetched are “rare Earth” theories that posit aliens might not exist because the conditions that allowed humans the time to evolve are very rare. One such possible condition is the existence of a moon that can help stabilize a planet's rotational axis because an unstable axis implies a wildly fluctuating climate.

Lock and Stewart state that synestias might be the norm in new planetary systems. If they are indeed common, does this increase or decrease the probability that extrasolar planets might have a “dual planet” system (akin to our Earth and moon)?


THE AUTHORS REPLY: Although synestias are common, not all of them will form a large moon. They come in a wide variety of shapes, sizes, and thermal and rotational states. Key to the size of the satellite that can be formed from a synestia is the amount of mass that is injected into orbit in the outer regions of the body. Only a small fraction of impacts will inject enough mass into orbit to form a moon as large as ours, and we are still working out what range of conditions could make it.

Synestias are a new part of the grand mystery of how rare life on Earth is. And whether a “dual planet” system like our own is common is still very much an open question. We will keep working to understand which of our planet's special characteristics were determined during its formation.


I read “Mapping the Mission,” Edward Bell's breakdown of Apollo 11's landing, with great interest. Could you clarify what happened to the equipment and to the Stars and Stripes banner that was left on the moon's surface? Were they blown away by the exhaust gases and hidden by dust when the explorers departed in the lunar module?


THE EDITORS REPLY: According to NASA, the American flag indeed was likely knocked over by the rocket blast as the lunar module lifted off from the moon. Either way, its stars and stripes are probably long gone, faded by the intense ultraviolet radiation on our natural satellite. The lunar module's descent stage and scientific instruments are thought to remain on the moon, albeit weathered by micrometeorites, radiation and extreme temperature changes.


“Lunar Land Grab,” by Adam Mann, should have said that 109 countries are now party to the Outer Space Treaty, not 107. Additionally, the article refers to 2012 as the original deadline for the Google Lunar XPRIZE. To clarify: in the initial competition, participants had until the end of that year to win the full grand prize, after which a reduced prize would be available until the end of 2014.