SUNSET: 
Mars Hosted Supervolcanoes in the Ancient Past
Scientists have found massive ash deposits that formed over millions of years of volcanic super-eruptions, the first evidence for such explosive activity on Mars.
NASA’s Curiosity Takes Step Toward Solving Mars Methane Mystery
New measurements from NASA’s Curiosity rover show that methane concentrations near the Martian surface vary on a daily cycle. The finding could help reconcile conflicting data.
Radioactive Aluminum Sheds Light on Solar System History
Astronomers thought giant stars were reponsible for flooding the early system with a radioative isotope — but the Sun itself might have made it.
Long-lived Lunar Magma Ocean Points to a Younger Moon
Most lunar scientists today think that the Moon formed after a Mars-size body hit the still-forming Earth, launching enough material into orbit to form our satellite. But there is still lively debate about the age of the Moon, and its evolution after it formed. A Mars-size body smashed into Earth…
Why Have Parts of Mercury's Landscape "Deflated"?
A type of landscape on Mercury known as “chaotic terrain” might have released materials stored underground for eons.
New Horizons Reveals Full Picture of Arrokoth...and How Planets Form
New Horizon’s flyby of Arrokoth, a planetesimal in the Kuiper Belt, reveals a pristine object untouched since the solar system’s origin. Its shape and geology show that planetesimals form more gently than previously thought.
The Clouds of Venus Puzzle Scientists
Japan’s Akatsuki spacecraft has revealed some previously unknown dynamics in the Venusian atmosphere, but their origin is far from clear.
A Possible Solution to Mars’s Methane Problem
A small amount of seepage could explain conflicting measurements of methane in the Martian atmosphere.
Could a Long-Ago Collision Explain Our Two-Faced Moon?
New research shows that a planetoid impact could have made our Moon asymmetric.
Apollo-era Data Reveal Moon’s Tectonic Activity
A new look at old seismic data gathered during the Apollo missions reveals young active faults as a possible origin of shallow moonquakes.
What the First Marsquake Means for NASA's Insight
After two months, InSight’s seismometer has picked up the first rumblings in Martian soil. Turns out marsquakes may be less frequent than thought.
The Martian Methane Mystery Continues
The most advanced instrument ever sent to Mars to study its atmosphere has failed to find any methane after months of searching.
New Study Confirms Methane on Mars – But It’s Not Definitive
Independent methane detections in the Martian atmosphere by the Curiosity rover and Mars Express orbiter add confusion to a convoluted story.
Hayabusa 2 Finds Asteroid Ryugu Is Dark & Dry
Hayabusa 2’s asteroid Ryugu has some unexpected characteristics. In particular, its dry surface could spell trouble for current theories about how Earth obtained its water.
Bumpy Road Ahead For NASA’s Osiris-REX
Asteroid Bennu is turning out to be a hazardous place for the NASA spacecraft to sample: It has uneven, rugged terrain and occasionally even hurls rocks into space.
Asteroid Impacts Increased 290 Million Years Ago, Lunar Craters Reveal
Researchers have estimated the ages of craters on the lunar surface, finding that the rate of large impacts nearly tripled 290 million years ago — an increase that might be ongoing.
Four Things We Now Know About Saturn
Cassini gave an epic final show, going where no space probe had gone before. Here are a few interesting things we learned from that finale.
'Oumuamua’s Story Keeps Spinning
Two new studies question the cometary nature of 'Oumuamua, our first interstellar visitor, and where in the Galaxy it might have come from.
'Oumuamua Was a Comet After All
Researchers have found that 'Oumuamua — the first confirmed object to enter the solar system from interstellar space — was a comet, releasing just enough gas to subtly change its course.
No Planet Nine? Small-body Pile-up Could Explain Odd Orbits
New research shows that interactions between small objects beyond Neptune’s orbit —and not a hypothetical Planet Nine — could be the reason some far-flung solar system objects “detach” from their original orbits.