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Enlarge / Artist's view of what InSight looked like after landing. (credit: NASA/JPL-Caltech)
Mars appears to be a frozen expanse of red dust, gaping craters, and rocky terrain on the outside—but what lies beneath its wind-blasted surface? NASA’s InSight lander might have discovered this before it took its proverbial last breaths in a dust storm.
Whether the core of Mars is solid or liquid has been long debated. While there is no way to observe the Martian core directly, InSight tried. Its seismometer, SEIS, was the first instrument to find possible evidence of a liquid core. In the meantime, its RISE (Rotation and Interior Structure Experiment) instrument had been measuring minuscule changes in the planet’s rotation as it orbited, “wobbles” in its axis caused by the push and pull of the Sun’s gravity.
“Our analysis of InSight’s radio tracking data argues against the existence of a solid inner core and reveals the shape of the core, indicating that there are internal mass anomalies deep within the mantle,” write the researchers behind the instrument in a study recently published in Nature.
Enlarge / Artist concept of Demonstration for Rocket to Agile Cislunar Operations (DRACO) spacecraft. (credit: DARPA)
Nearly three years ago, the US Defense Advanced Research Projects Agency announced its intent to develop a flyable nuclear thermal propulsion system. The goal was to develop more responsive control of spacecraft in Earth orbit, lunar orbit, and everywhere in between, giving the military greater operational freedom in these domains.
The military agency called this program a Demonstration Rocket for Agile Cislunar Operations, or DRACO for short. The program consists of the development of two things: a nuclear fission reactor and a spacecraft to fly it. In 2021, DARPA awarded $22 million to General Atomics for the reactor and gave small grants of $2.9 million to Lockheed Martin and $2.5 million to Blue Origin for the spacecraft system.
At the same time, NASA was coming to realize that if it were really serious about sending humans to Mars one day, it would be good to have a faster and more fuel-efficient means of getting there. An influential report published in 2021 concluded that the space agency's only realistic path to putting humans on Mars in the coming decades was using nuclear propulsion.
The search for life on other planets has been based on what we already know. But what if extraterrestrial life does not look like any beings we’re used to on Earth? It may even be unrecognizable to the scientists searching for it. In this essay, Sarah Scoles meets Sarah Stewart Johnson, who has been looking for “aliens” from a different perspective.
Even when scientists do discover biology unfamiliar to them, they tend to relate it to something familiar. For instance, when Antonie van Leeuwenhoek saw single-celled organisms through his microscope’s compound lens in the 17th century, he dubbed them “animalcules,” or little animals, which they are not.
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