Did you know that AAPG has an Astrogeology Committee? I attended their meeting last month. “The Astrogeology Committee provides AAPG members with a forum to discuss astrogeology and its relationships to terrestrial geology, energy, and other issues.” In the spirit of this mission, we’ll talk about planetary geology this week.
Rasoul Sorkhabi
Editor, Core Elements
Five Recent Revolutions in Astrogeology
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Alan Stern, a planetary scientist, examines five top planetary revolutions over the past 30 years in the September issue of Astronomy.
Discovery of the Kuiper Belt: The Kuiper Belt, named after the Dutch astronomer Gerard Kuiper who conjectured its existence in 1951, is a belt of dwarf planets (including Pluto) and frozen bodies, beyond the orbit of Neptune at 30 to roughly 50 astronomical units from the Sun.
Discovery of Exoplanets: So far, various telescopes and other methods have discovered nearly 6,000 exoplanets.
Perhaps the most novel and powerful method used by the James Webb Space Telescope is the transit method.
When a planet passes in front of its parent star—from our viewpoint, it moves behind the star and then reappears—its size, orbital period, and atmospheric composition can be determined by spectroscopy.
Transmission spectroscopy works by comparing starlight and combined star-planet light then subtracting the planet’s infrared light during its dayside.
Discovery of “ocean worlds:” These worlds arewater beneath the surface of moons in the Solar System. They include Enceladus and Titan (circling Saturn), as well as Callisto, Ganymede, and Europa (circling Jupiter).
The rise of PI-led missions: Some of NASA’s space missions are now led by Principal Investigators (usually scientists), rather than Project Managers.
The rise of commercial spaceflights: Commercial involvement in space missions, satellite communications, and rocket launching is a new and growing venture. SpaceX (Elon Musk), Blue Origin (Jeff Bezos), and Rocket Lab (Peter Beck) are only some of these space companies.
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Another article in Astronomyintroduces the lives and works of 10 women who have made transformative contributions to astronomy. Let’s take a look.
Caroline Herschel (1750–1848): One of the first professional astronomers, she discovered eight comets, 500 stars, and 2,500 nebulae.
She first worked with her astronomer brother William Herschel in England.
After William’s death in 1822, Caroline returned to her home country of Germany and helped her son, John, become an astronomer.
Maria Mitchell (1818–1889): Mitchell was the first female American astronomer, and the first American to discover a comet known as C/1847 T1 or Miss Mitchell’s comet.
She worked at the U.S. Naval Laboratory and taught at Vassar College.
Annie Jump Cannon (1863–1941): She graduated from Radcliffe College, then worked for Harvard Observatory’s Director Edward Pickering.
Cannon classified 350,000 stars and developed the Harvard System of spectral classification that’s still used today.
Henrietta Swan Leavitt (1868–1921): She also graduated from Radcliffe College and worked at Harvard Observatory.
Leavitt helped find a relationship between the brightness and the period of Cepheid variables to determine distances between celestial bodies.
Her work was recognized long after her death at age 53 in Massachusetts.
Cecilia Payne-Gaposchkin (1900–1979): She was born in England and studied at Harvard under Harlow Shapley (Pickering’s successor).
She discovered that stars are made up of hydrogen and helium—the subject of her PhD thesis.
Nancy Grace Roman (1925–2018): Nicknamed the “Mother of Hubble Space Telescope,” Roman obtained a PhD from the University of Chicago and became the first chief of astronomy at NASA in 1961.
Vera Rubin (1928–2016): Recognized for her discovery of dark matter, Rubin was a professor at Georgetown University.
Carolyn Shoemaker (1929–2021): She discovered dozens of asteroids and comets, including the Comet Shoemaker-Levy 9.
She also worked closely with her husband Gene Shoemaker, who was also an astronomer.
Jocelyn Bell Burnell (1943–present): Born in Belfast, Ireland, she discovered “pulsars” in 1960 by observing signals coming from rapid neutron stars.
Andrea M. Ghez (1965–present): She received the 2020 Nobel Prize in physics for her discovery of a supermassive black hole at the center of our galaxy.
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An article in The Atlantic discusses the rise of Elon Musk’s SpaceX in the context of NASA’s history.
Flashback on NASA:
NASA was established in 1958 as the United States concentrated efforts to become the leading power in the “New Frontier” of space technology and exploration.
In the 1960s, at the height of the Cold War, NASA was well funded and grew rapidly as per President John F. Kennedy’s vision of “landing a man on the Moon.”
Go deeper: Only 628 people in human history have left Earth. Tim Peake’s Space: The Human Story discusses the lives of the astronauts. Recently NASA selected 10 new American astronaut candidates (including six women) out of more than 8,000 applicants.
The Rise of SpaceX:
SpaceX was established in 2022, and its initial growth was essentially due to U.S. funds in 2006 and 2010.
Last year, 95 percent of the space rockets launched from the United States were conducted by SpaceX.
SpaceX has put nearly 8,000 communication satellites into orbit around Earth. SpaceX technology is “becoming indispensable” to U.S. space power.
SpaceX’s reusable rocket Falcon 9 has revolutionized space technology.
SpaceX’s dream is to send human space missions to Mars.
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