Did a giant object collide with Earth to form the moon?

space.com Oct 19, 2026

Did a giant object collide with Earth to form the moon?

Curated by Shubham · TechCapsules · Oct 19, 2026

AI-summarised brief · reviewed before publication

Astronomers now regard the giant‑impact hypothesis as the leading explanation for the Moon’s origin. The theory posits that, within the first 100 million years of the solar system, a Mars‑sized protoplanet dubbed Theia collided with the proto‑Earth, ejecting mantle material that coalesced into the Moon in a matter of hours. The idea traces back to Reginald Daly’s 1946 suggestion of an impact origin, gained traction in the 1970s through William Hartmann and Donald Davis’s collision models, and was cemented at a 1984 conference in Kona, Hawaii. Supporting evidence includes matching stable‑isotope ratios between Earth and lunar rocks, the Earth‑Moon system’s unusually high angular momentum, the Moon’s small iron core, low density, and depletion of volatile elements—signatures consistent with a high‑energy, planetary‑scale blast.

💡 Why It Matters

· The hypothesis links the Moon’s unique physical traits directly to a single, violent event, reshaping our understanding of early Earth dynamics and planetary formation.

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On this day in space! Oct. 19, 2016: Europe’s ExoMars orbiter and…

On October 19, 2016, the European Space Agency’s ExoMars mission reached Mars, deploying the Trace Gas Orbiter and the Schiaparelli lander. The orbiter entered Martian orbit after a successful separation, while the lander crashed during descent, losing all contact one minute before touchdown. The orbiter remains operational, surveying methane and other gases in the atmosphere. The lander’s failure, attributed to a data glitch, delayed the planned 2018 rover launch and prompted ESA to reassess its partnership with Russia.

💡 The loss of Schiaparelli exposed critical vulnerabilities in Mars landing systems, reshaping ESA’s risk management and delaying future exploration plans.

space.com · Oct 19

Japan launches historic MMX sample-return mission to Mars’ moon Phobos (video)

Japan’s Martian Moons eXploration (MMX) mission lifted off from Tanegashima on Oct. 19 aboard a JAXA‑Mitsubishi H3 rocket, beginning a ten‑month trek to Mars. The 63‑metre launch vehicle performed a flawless ascent, shedding boosters, fairings and executing a trans‑Mars injection burn that placed MMX on a 24,145 mph trajectory toward the Red Planet. Scheduled to arrive in August 2027, the spacecraft will enter a quasi‑satellite orbit around Phobos, conduct a three‑year campaign that includes two landings on the 22‑km moon, sample collection, and a rover deployment by French‑German partners. After a brief Phobos return, MMX will fly by Deimos before departing for Earth in November 2030, with a return capsule slated to touch down in Australia in 2031.

💡 Retrieving Phobos material could finally resolve the long‑standing debate over whether Mars’ moons formed from an impact or were captured asteroids, offering a rare glimpse into early solar‑system processes.

spacenews.com · Oct 19

UARX Space troubleshoots anomalies on maiden OTV Flight

Spanish startup UARX Space is addressing anomalies discovered during the maiden flight of its 200‑kilogram orbital transfer vehicle OSSIE‑D, launched on Oct. 1 aboard SpaceX’s Transporter‑18 mission. A communications blackout occurred immediately after launch, traced to a ground‑station interface configuration error. UARX sent a backup command two days later to trigger autonomous fault detection, isolation and recovery, allowing payload deployment without ground contact. After correcting the error, two‑way communications were restored, telemetry confirmed receipt of the command and successful release of at least ten PocketQubes for customers including AMSAT‑Deutschland, Libre Space Foundation and DIYSatellite. Additional hosted payloads remain onboard, with further deployments scheduled in the coming weeks. UARX plans to use the flight data to refine its software and certify missions.

💡 The swift autonomous recovery proves that small launch providers can protect customer payloads even when ground links fail, reinforcing trust in low‑cost rideshare missions.

space.com · Oct 19

‘They’re kind of goth’: NASA spacecraft gives mysterious brown dwarfs a close-up

NASA’s SPHEREx spacecraft has delivered the most detailed spectral survey to date of 37 nearby brown dwarfs, objects that bridge the gap between giant planets and stars. By capturing light across 102 wavelengths—from visible red to infrared—researchers identified abundant water, carbon dioxide, carbon monoxide and methane in their atmospheres and observed how these signatures shift with temperature, which ranges from about 2,200 °C down to –20 °C. The data reveal that some brown dwarfs are undergoing rapid cloud‑clearing, exposing methane‑rich layers, while others display distinct spectral profiles despite similar temperatures. The study, led by Caltech’s Zafar Rustamkulov and J. Davy Kirkpatrick, demonstrates SPHEREx’s unique capability to probe atmospheric chemistry that ground‑based telescopes cannot see, and it opens a path to analyze thousands more free‑floating objects.

💡 By directly measuring the chemical makeup of isolated brown dwarfs, SPHEREx provides a rare benchmark for testing atmospheric models of sub‑stellar objects, sharpening our understanding of planetary‑mass atmospheres beyond the solar system.

space.com · Oct 19

Japan launching bold sample-return mission to Mars moon Phobos today: Watch it…

Japan’s space agency JAXA is set to launch the Martian Moons eXploration (MMX) mission today, Oct. 19, at 3:41 p.m. EDT aboard an H3 rocket from Tanegashima. The spacecraft will travel to Mars, arrive in August 2027, and enter orbit around Phobos a month later. Over the next 18 months it will survey Phobos and Deimos before deploying the ESA‑led Idefix rover on Phobos in early 2029 to assess landing conditions and surface composition. The mothership will attempt a controlled touchdown in 2030, collect at least 10 g of regolith, and return the sample to Earth in 2031. NASA contributes a scientific instrument, communications support and funding for U.S. researchers, while the mission builds on Japan’s Hayabusa sample‑return heritage and international collaboration.

💡 Returning Phobos material could finally settle the moons’ origin, shedding light on how water and organic compounds were delivered to the inner planets.

space.com · Oct 18

Returning the first samples from a Martian moon: Inside the science of…

Japan’s Martian Moons eXploration (MMX) mission will launch on an H3 rocket from Tanegashima on Oct. 19, aiming to become the first spacecraft to return samples from Mars orbit. After a ten‑month cruise, MMX will enter Mars orbit in August 2027, spend three years studying Phobos, deploy the IDEFIX rover, and collect surface material that could be the inaugural samples from the Mars system. The probe will then conduct flybys of Deimos before departing for Earth in November 2030, with a sample‑return capsule slated to land in Australia in 2031. MMX’s three modules—propulsion, exploration (housing instruments such as MEGANE, MIRS, TENGOO, OROCHI, LIDAR and a mass spectrometer) and return—are built by Mitsubishi Electric, with key scientific hardware contributed by NASA, CNES and DLR.

💡 The mission will deliver pristine Martian‑moon material to Earth, offering a unique window into the early solar system and the origin of Phobos and Deimos.