Astropulse: A New Way for ET to Phone Home

Episode Summary

Executive Summary: This Planetary Radio episode blends membership promotion with three main science themes: the search for extraterrestrial intelligence, NASA’s human-spaceflight politics, and Mars Phoenix mission science. Dan Wertheimer explains SETI@home’s new AstroPulse search for broad radio pulses, Bill Nye argues for preserving U.S. crewed-launch capability despite shuttle retirement and budget constraints, and Emily Lakdawalla answers why Mars’ atmospheric pressure is falling. Bruce Betts closes with skywatching, asteroid trivia, and a space history note.

Main Topics: SETI@home and the AstroPulse search (Priority: 5/5): Dan Wertheimer describes a new SETI search for radio pulses rather than only narrowband continuous signals, using the distributed computing power of about a million volunteers and data from Arecibo. Human spaceflight policy and shuttle retirement (Priority: 5/5): Bill Nye discusses the aging Space Shuttle, potential gaps in U.S. crewed access to space, Russia/Europe/Canada’s roles, and the need to weigh the issue in the public and political sphere. Mars Phoenix atmospheric pressure drop (Priority: 4/5): Emily Lakdawalla explains that Phoenix measurements show pressure falling because carbon dioxide is freezing out at Mars’ south pole, outweighing local sublimation effects at the north pole. Night sky observing and space history (Priority: 3/5): Bruce Betts offers observational tips for Jupiter, Venus, Mercury, Mars, and Uranus, plus a space-history note on Lost in Space. Asteroid and comet exploration context (Priority: 3/5): Betts highlights Rosetta’s flyby of asteroid Steins and the broader scale differences among visited asteroids, emphasizing how spacecraft missions have expanded knowledge of small bodies. Planetary Society engagement and outreach (Priority: 4/5): The episode repeatedly promotes membership, t-shirt incentives, reviews, and volunteer computing participation to support Planetary Society and SETI efforts.

Key Arguments: SETI should search for multiple signal types because extraterrestrial intelligence may not transmit the way humans expect; AstroPulse adds pulse searches to narrowband work. Pulse signals can be missed by traditional SETI methods, so a dedicated high-sensitivity search could reveal ET, black-hole events, or unknown astrophysical phenomena. The Allen Telescope Array’s many small dishes provide a scalable, wide-field, lower-cost alternative to traditional large-dish radio astronomy. Bill Nye argues that crewed space access matters politically and symbolically even though NASA’s budget is small relative to the federal budget. A temporary U.S. gap in crew launch capability is not necessarily a crisis, but it should still be considered seriously by voters and taxpayers. Mars pressure is dropping globally because seasonal CO2 freeze-out at the south pole reduces atmospheric pressure across the planet, despite summertime sublimation at Phoenix’s landing site.

Data Points: SETI@home volunteers: about 1 million - Dan Wertheimer says the project relies on roughly a million volunteers, making it the world’s largest supercomputer. Allen Telescope Array dishes: 42 currently connected - Wertheimer notes the ATA is scalable and can add more dishes over time. ATA dish size: 20 feet across / 6 meters - Describing the small dishes used in the Allen Telescope Array. Arecibo beam width: about 1/20 of a degree - Wertheimer contrasts Arecibo’s narrow field of view with the ATA’s wider sky coverage. SETI searches: 7 simultaneous searches - Wertheimer explains the project uses multiple strategies to detect possible extraterrestrial signals. Mars air pressure at Phoenix landing: 8.5 millibars maximum - Emily Lakdawalla cites Phoenix’s measured peak pressure on landing day. Phoenix pressure change: more than 10% decrease - Pressure has continued to fall since landing at Mars’ north polar region. Martian atmosphere composition: 99% carbon dioxide - Used to explain why seasonal freeze-out at the south pole affects global pressure. NASA budget: about 0.5% of U.S. government budget - Bill Nye uses this to argue that space policy receives disproportionate attention relative to funding. Ares I milestone: preliminary design review passed - Mentioned at the start as a significant step for the human-rated U.S. rocket. Human-rated American rocket design review gap: 35 years - This is described as the first such review in decades. Spacecraft/asteroid systems visited: 8 asteroid systems and 9 asteroids - Bruce Betts summarizes the Rosetta/asteroid visitation landscape. Asteroid Itokawa size: 500 meters by 200 meters - Used in Betts’s comparison of visited small bodies. Asteroid Matilda size: 66 km by 44 km - Used to show the range in asteroid sizes visited by spacecraft. Contested trivia deadline: Monday, September 22 at 2 p.m. Pacific - Deadline given for entering the Planetary Radio trivia contest.

Pivotal Quotes: "Our idea is to try multiple strategies. We don't know what kind of signal ET might be sending... we want to do a lot of different searches." — Dan Wertheimer: Explaining why SETI@home is adding the AstroPulse pulse search alongside other methods. "The prestige associated with space transportation and humans in space is somehow out of proportion to the amount of money available." — Bill Nye: Arguing that crewed spaceflight has symbolic importance despite limited funding. "The reason it's decreasing has to do with a pole, but not the North Pole. It's actually the South Pole that's controlling Mars' atmospheric pressure." — Emily Lakdawalla: Answering why Phoenix measured falling air pressure on Mars.

Implications: The episode underscores how citizen computing, diversified search strategies, and public engagement can expand scientific discovery. It also frames crewed spaceflight as a policy choice with symbolic weight, while showing how Mars and asteroid missions continue to refine planetary science.