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Around 4 billion years ago, an asteroid hit the Jupiter moon Ganymede. Now, a Kobe University researcher realized that the Solar System’s biggest moon’s axis has shifted as a result of the impact, which confirmed that the asteroid was around 20 times larger than the one that ended the age of the dinosaurs on Earth, and caused one of the biggest impacts with clear traces in the Solar System.

Ganymede is the largest moon in the Solar System, bigger even than the planet Mercury, and is also interesting for the liquid water oceans beneath its icy surface. Like the Earth’s moon, it is tidally locked, meaning that it always shows the same side to the planet it is orbiting and thus also has a far side. On large parts of its surface, the moon is covered by furrows that form concentric circles around one specific spot, which led researchers in the 1980s to conclude that they are the results of a major impact event. “The Jupiter moons Io, Europa, Ganymede and Callisto all have interesting individual characteristics, but the one that caught my attention was these furrows on Ganymede,” says the Kobe University planetologist HIRATA Naoyuki. He continues, “We know that this feature was created by an asteroid impact about 4 billion years ago, but we were unsure how big this impact was and what effect it had on the moon.”

Data from the remote object is scarce making research very difficult, and so Hirata was the first to realize that the purported location of the impact is almost precisely on the meridian farthest away from Jupiter. Drawing from similarities with an impact event on Pluto that caused the dwarf planet’s rotational axis to shift and that we learned about through the New Horizons space probe, this implied that Ganymede, too, had undergone such a reorientation. Hirata is a specialist in simulating impact events on moons and asteroids, so this realization allowed him to calculate what kind of impact could have caused this reorientation to happen.

How did a giant impact 4 billion years ago affect Jupiter’s moon, Ganymede? This is what a recent study published in Scientific Reports hopes to address as a researcher from Kobe University investigated the geological changes known as a “furrow system” that Ganymede has exhibited since being struck by a giant asteroid in its ancient past, along with confirming previous hypotheses regarding the size of the asteroid. This study holds the potential to help scientists better understand how the very-active early solar system not only contributed to Ganymede’s but how such large impacts could have influenced the evolution of planetary bodies throughout the solar system.

“The Jupiter moons Io, Europa, Ganymede and Callisto all have interesting individual characteristics, but the one that caught my attention was these furrows on Ganymede,” said Dr. Naoyuki Hirata, who is an assistant professor in the Department of Planetology at Kobe University and sole author of the study. “We know that this feature was created by an asteroid impact about 4 billion years ago, but we were unsure how big this impact was and what effect it had on the moon.”

For the study, Dr. Hirata used a series of mathematical calculations to ascertain the size of the object that impacted Ganymede billions of years ago along with the angle of impact that produced the furrow system. In the end, Dr. Hirata determined that the impactor’s radius was approximately 93 miles (150 kilometers) and the angle of impact was potentially between 60 to 90 degrees, resulting in the furrows that overlay a significant portion Ganymede’s surface. For context, Ganymede is not only the largest moon in the solar system at a radius of 1,637 miles (2,634 kilometers), but it is also larger than the planet Mercury.

A new study looking at the potentially hazardous asteroid 99,942 Apophis has suggested that the odds of an impact in 2029 or 2036 is ever so slightly higher than we thought.

When Apophis was first discovered in 2004, observations briefly placed it at level 4 on the Torino impact hazard scale, with a score of 0 meaning the likelihood of impact is zero or thereabouts, and 10 meaning “a collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization as we know it, whether impacting land or ocean.”

While level 4 might sound low, it is the highest level of any object that has been discovered since NASA first started monitoring potentially hazardous Near-Earth Objects (NEOs).

The asteroid Apophis, named after the Egyptian god of chaos, was discovered in 2004. Early calculations raised concerns due to its potential collision with Earth, making it a focus for scientists.

A space rock that smacked into Earth 66 million years ago and devastated the ancient life living thereon took a remarkably circuitous route to get here, a new study has found.

The Chicxulub event – the giant impact that ended the reign of non-avian dinosaurs, clearing the way for mammalian life to rise – was triggered by an asteroid from a region of the Solar System out past the orbit of Jupiter, the cold, dark outer limits, far from the Sun’s light and warmth.

And an asteroid it was indeed, with the new findings by an international team of researchers ruling out that the object could have been a comet.

“The NEOWISE mission has been an extraordinary success story as it helped us better understand our place in the universe by tracking asteroids and comets that could be hazardous for us on Earth,” Nicola Fox, associate administrator for the Science Mission Directorate at NASA Headquarters, said in a statement on Thursday.

“While we are sad to see this brave mission come to an end, we are excited for the future scientific discoveries it has opened by setting the foundation for the next generation planetary defense telescope,” she added.

NEOWISE launched in December 2009 with a different name and a different mission. Originally called WISE (Wide-field Infrared Survey Explorer), the probe scanned the entire infrared sky over the course of a seven-month prime mission. It did so “with far greater sensitivity than previous surveys,” NASA officials wrote in the same statement.

What would it take to set Uranus ablaze? Is it even possible to burn it in the typical sense? If anyone can figure it out, it’s the Dead Planets Society.

Join Dead Planeteers Leah and Chelsea as they invite planetary scientist Paul Byrne back to the podcast, to join in more of their chaotic antics.

Continue reading “Can We Burn Uranus? | Dead Planets Society Podcast” »

BUSAN, South Korea — The European Space Agency will allow a proposed mission to the asteroid Apophis to proceed to a next stage of development to keep it on schedule even though it is not yet fully funded.

ESA announced July 16 that its space safety program, which includes planetary defense, has given the Ramses mission permission to begin preparatory work for the mission, which is designed to visit Apophis before that asteroid makes a very close flyby of Earth in April 2029.

Ramses, or Rapid Apophis Mission for Space Safety, would use the same spacecraft bus as ESA’s Hera mission, scheduled to launch this October to visit the asteroid Didymos, whose moon Dimorphos was the target of NASA’s DART mission to deflect its orbit. Ramses will carry two cubesats for additional studies of the asteroid.

30 years ago, on 16 July 1994, astronomers watched in awe as the first of many pieces of the Shoemaker-Levy 9 comet slammed into Jupiter with incredible force. The event sparked intense interest in the field of planetary defence as people asked: “Could we do anything to prevent this happening to Earth?”

Today, ESA’s Space Safety programme takes another step towards answering this question. The programme has received permission to begin preparatory work for its next planetary defence mission – the Rapid Apophis Mission for Space Safety (Ramses).

Ramses will rendezvous with the asteroid 99,942 Apophis and accompany it through its safe but exceptionally close flyby of Earth in 2029. Researchers will study the asteroid as Earth’s gravity alters its physical characteristics. Their findings will improve our ability to defend our planet from any similar object found to be on a collision course in the future.