ALH84001, which is one of the most famous meteorites ever recovered, helped catapult the field of astrobiology to new heights when scientists uncovered what initially appeared to be microscopic bacteria fossils within this meteorite, though those findings remain inconclusive to this day. (Credit: NASA)
Universe Today has explored the importance of studying impact craters, planetary surfaces, exoplanets, astrobiology, solar physics, comets, planetary atmospheres, planetary geophysics, and cosmochemistry, and how this myriad of intricately linked scientific disciplines can assist us in better understanding our place in the cosmos and searching for life beyond Earth. Here, we will discuss the incredible research field of meteorites and how they help researchers better understand the history of both our solar system and the cosmos, including the benefits and challenges, finding life beyond Earth, and potential routes for upcoming students who wish to pursue studying meteorites. So, why is it so important to study meteorites?
A June 2020 artist illustration of NASA's Psyche spacecraft. (Credit: NASA/JPL-Caltech/Arizona State University)
NASA’s Psyche mission is back on track for launch and is now scheduled for a potential October 2023 launch date, according to an October 2022 statement from NASA. This comes after missing its originally planned launch date between August and October of 2022, and becoming subject to an independent review board, whose results were announced in November 2022.
In a recent study accepted to The Astrophysical Journal Letters, a team of researchers at the University of Nevada, Las Vegas (UNLV) investigated the potential for life on exoplanets orbiting M-dwarf stars, also known as red dwarfs, which are both smaller and cooler than our own Sun and is currently open for debate for their potential for life on their orbiting planetary bodies. The study examines how a lack of an asteroid belt might indicate a less likelihood for life on terrestrial worlds.
Artist's impression of the asteroid belt. Image credit: NASA/JPL-Caltech
Earth formed over 4.5 billion years ago via accretion. Earth’s building blocks were chunks of rock of varying sizes. From dust to planetesimals and everything in between. Many of those chunks of rock were carbonaceous meteorites, which scientists think came from asteroids in the outer reaches of the main asteroid belt.
But some evidence doesn’t line up well behind that conclusion. A new study says that some of the Earth-forming meteorites came from much further out in the Solar System.
A United Launch Alliance Atlas V rocket with the Lucy spacecraft aboard is seen at Space Launch Complex 41, Thursday, Oct. 14, 2021, at Cape Canaveral Space Force Station in Florida. Credit: NASA/Bill Ingalls.
An early morning launch is planned for the Lucy spacecraft, the first space mission to study Jupiter’s Trojan asteroids. Tomorrow, October 16 at 5:34 a.m. EDT is the first day and time in Lucy’s 21-day launch window, and current weather conditions show a 90% chance of favorable conditions for liftoff from Cape Canaveral Space Force Station in Florida. The launch window remains open for 75 minutes.
Lucy will embark on a 12-year mission to explore the “fossils of planet formation,” Jupiter’s Trojan asteroid swarms. This mission provides the first opportunity to observe these intriguing objects close-up.
In astronomy, comets and asteroids are defined very differently. Comets have a “nucleus,” usually made of ice and dust, and a tail when they get near the sun, which is the nucleus material shedding off from the comet itself. Asteroids, on the other hand, are small balls of rock orbiting the sun. Occasionally though, some objects meet the criteria to be both an asteroid and a comet – and a team from the Planetary Science Institute (PSI) think they have found a new one.
How do you track an asteroid that hit the Earth over 60 million years ago? By using a combination of geology and computer simulations, at least according to a team of scientists from the Southwest Research Institute (SwRI). Those methods might have let them solve a long-standing mystery of both archeology and astronomy – where did the asteroid that killed the dinosaurs come from?
If asked to pick what color asteroids in the asteroid belt would be, red is likely not one that would come to mind for most people. But that is exactly the color of two new asteroids found by Hasegawa Sunao of JAXA and an international team of researchers. The catch is the objects don’t appear to be from the asteroid belt at all, but are most likely Trans-Neptunian objects that were somehow transported into what is commonly thought of as the asteroid belt. How exactly they got there is still up for debate.
An artist's conception of an NEO asteroid orbiting the Sun. Credit: NASA/JPL.
Astronomers have painstakingly built models of the asteroid population, and those models predict that there will be ~1 km sized asteroids that orbit closer to the Sun than Venus does. The problem is, nobody’s been able to find one. Until now.
Astronomers working with the Zwicky Transient Facility say they’ve finally found one. But this one’s bigger, at about 2 km. If its existence can be confirmed, then asteroid population models may have to be updated.
A view of Ceres in natural colour, pictured by the Dawn spacecraft in May 2015. Credit: NASA/ JPL/Planetary Society/Justin Cowart
In March of 2015, NASA’s Dawn mission arrived around Ceres, a protoplanet that is the largest object in the Asteroid Belt. Along with Vesta, the Dawn mission seeks to characterize the conditions and processes of the early Solar System by studying some of its oldest objects. One thing Dawn has determined since its arrival is that water-bearing minerals are widespread on Ceres, an indication that the protoplanet once had a global ocean.
Naturally, this has raised many questions, such as what happened to this ocean, and could Ceres still have water today? Towards this end, the Dawn mission team recently conducted two studies that shed some light on these questions. Whereas the former used gravity measurements to characterize the interior of the protoplanet, the latter sought to determine its interior structure by studying its topography.
Ceres. as imaged by the NASA Dawn probe. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Together, the team relied on gravity measurements of the protoplanet, which the Dawn probe has been collecting since it established orbit around Ceres. Using the Deep Space Network to track small changes in the spacecraft’s orbit, Ermakov and his colleagues were able to conduct shape and gravity data measurements of Ceres to determine the internal structure and composition.
What they found was that Ceres shows signs of being geologically active; if not today, than certainly in the recent past. This is indicated by the presence of three craters – Occator, Kerwan and Yalode – and Ceres’ single tall mountain, Ahuna Mons. All of these are associated with “gravity anomalies”, which refers to discrepancies between the way scientists have modeled Ceres’ gravity and what Dawn observed in these four locations.
The team concluded that these four features and other outstanding geological formations, are therefore indications of cryovolcanism or subsurface structures. What’s more, they determined that the crust’s density was relatively low, being closer to that of ice than solid rock. This, however, was inconsistent with a previous study performed by Dawn guest investigator Michael Bland of the U.S. Geological Survey.
Bland’s study, which was published in Nature Geoscience back in 2016, indicated that ice is not likely to be the dominant component of Ceres strong crust, on a count of it being too soft. Naturally, this raises the question of how the crust could be light as ice in terms of density, but also much stronger. To answer this, the second team attempted to model how Ceres’ surface evolved over time.
Gravity measurements of Ceres, which provided hints about its internal structure. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Their study, titled “The Interior Structure of Ceres as Revealed by Surface Topography and Gravity“, was published in the journal Earth and Planetary Science Letters. Led by Roger Fu, an assistant professor with the Department of Earth, Atmospheric and Planetary Sciences at MIT, this team consisted of members from Virginia Tech, Caltech, the Southwest Research Institute (SwRI), the US Geological Survey, and the INAF.
Together, they investigated the strength and composition of Ceres’ crust and deeper interior by studying the dwarf planet’s topography. By modeling how the protoplanet’s crust flows, Fu and colleagues determined that it is likely a mixture of ice, salts, rock, and likely clathrate hydrate. This type of structure, which is composed of a gas molecule surrounded by water molecules, is 100 to 1,000 times stronger than water ice.
This high-strength crust, they theorize, could rest on a softer layer that contains some liquid. This would have allowed Ceres’ topography to deform over time, smoothing down features that were once more pronounced. It would also account for its possible ancient ocean, which would have frozen and become bound up with the crust. Nevertheless, some of its water would still exist in a liquid state underneath the surface.
This theory is consistent with several thermal evolution models which were published before the Dawn mission arrived at Ceres. These models contend that Ceres’ interior contains liquid water, similar to what has been found on Jupiter’s moon Europa and Saturn’s moon Enceladus. But in Ceres’ case, this liquid could be what is left over from its ancient ocean rather than the result of present-day geological activity in the interior.
Diagram showing a possible internal structure of Ceres. Credit: NASA/ESA/STScI/A. Feild
Taken together, these studies indicate that Ceres has had a long and turbulent history. While the first study found that Ceres’ crust is a mixture of ice, salts and hydrated materials – which represents most of its ancient ocean – the second study suggests there is a softer layer beneath Ceres’ rigid surface crust, which could be the signature of residual liquid left over from the ocean.
As Julie Castillo-Rogez, the Dawn project scientist at JPL and a co-author on both studies, explained, “More and more, we are learning that Ceres is a complex, dynamic world that may have hosted a lot of liquid water in the past, and may still have some underground.”
On October 19, 2017, NASA announced that the Dawn mission would be extended until its fuel runs out, which is expected to happen in the latter half of 2018. This extension means that the Dawn probe will be in orbit around Ceres as it goes through perihelion in April 2018. At this time, surface ice will start to evaporate to form a transient atmosphere around the body.
During this period and long after, the spacecraft is likely to remain in a stable orbit around Ceres, where it will continue to send back information on this protoplanet/large asteroid. What it teaches us will also go a long way towards informing our understanding of the early Solar System and how it evolved over the past few billion years.
In the future, it is possible that a mission will be sent to Ceres that is capable of landing on its surface and exploring its topography directly. With any luck, future missions will also be able to explore the interior of Ceres, and other “ocean worlds” like Europa and Enceladus, and find out what lurks beneath their icy surfaces!
