From the exploration of other planets to the meanderings of single cells through our bloodstream and into our tissues, Caltech and JPL researchers are thinking about transportation in unexpected ways. They’re using transformative delivery methods to land on Mars, collect data in hard-to-reach locales, and shepherd drugs to the brain.
For example, chemical engineer Mark Davis is building on his experience with nanomaterials to create a nanoparticle delivery vehicle that would encapsulate chemotherapeutics and carry them to where they are supposed to go in the body. These nanoparticles should stay in the blood until they reach a tumor and then release their payload, thus allowing the drugs to destroy solid tumors while sparing healthy tissue.
Lance Christensen, a senior atmospheric scientist at JPL, invents tunable laser spectrometers that basically sniff the atmosphere for trace measurements of gases. Such spectrometers can be carried on drones to measure the abundance of atmospheric gases such as methane, water vapor, and carbon dioxide.
And then there’s geochemist Ken Farley, the project scientist for Mars 2020, the new rover mission. He is helping define the science goals for the Mars 2020 mission and determining how to pack an assembly of all-new scientific instruments onto an existing rover. And he has to do all this in time to meet the “very hard” launch date of 2020—when Mars and Earth are closest in orbit to each other.
The overall focus for all of these researchers is to better be able to ask big questions about the origins of life, to monitor the earth’s emissions and overall health, and even to treat some of the most devastating diseases we encounter. For more about their efforts, read Special Delivery on E&S+.
Sending a spacecraft to Jupiter and into its extreme radiation environment—1,000 times more intense than Earth’s—is a daring endeavor. On the evening of July 4, 2016, engineers and scientists at NASA’s Jet Propulsion Laboratory in Pasadena put their ingenuity and years of efforts to the test as the Juno mission traveled through Jupiter’s radiation belts en route to the planet. Cheers erupted at JPL’s mission control at 8:53 p.m. Pacific Daylight Time, when Juno sent back signals indicating that the spacecraft had finished an engine burn that successfully placed it into orbit around Jupiter.
About an hour later, the mission team, clad in matching Juno polo shirts, entered JPL’s Von Kármán Auditorium to an outpouring of cheers. Several team members took the stage for a news briefing, where they reported on the status of Juno.
“It’s amazing, it feels wonderful, and it’s also just the beginning,” said JPL’s Juno Project Scientist Steve Levin, describing how it felt to have made it into orbit around Jupiter.
Juno is now the first spacecraft to ever orbit the poles of Jupiter, and it will have the closest orbit of any mission yet, descending to within 3,000 miles above the cloud tops. Previous missions to Jupiter such as NASA’s Voyager and Galileo spacecraft returned unprecedented images and data. However, those earlier probes orbited around the equator, leaving gaps in our maps and overall understanding of the solar system’s most massive planet.
The Juno probe is currently in a 53.5-day orbit around Jupiter, as its instruments are checked out. On October 19, it will begin its 14-day science orbits, and will begin to look into Jupiter’s clouds to investigate mysteries such as how this planet with a mass more than 300 times that of Earth formed. Juno will also gather information on the planet’s magnetosphere, an invisible bubble of trapped charged particles and radiation that would appear to be bigger than the sun if viewable from Earth.
Caltech’s Andrew Ingersoll, professor of planetary science and a Juno team member, says he is looking forward to the unexpected. Ingersoll has been involved with six other NASA missions—Pioneer Venus, Pioneer Saturn/Jupiter, Voyager 1 and 2, Mars Global Surveyor, Galileo, and Cassini.
“I live for the surprises,” Ingersoll says. For example, the Voyager 1 mission in the late 1970s discovered that Io, a moon of Jupiter, had volcanoes and molten lava. “It was mind-blowing,” he says.
This time, Ingersoll says he is most excited to address a question that has persisted for decades: how much water does Jupiter hold?
“We still don’t know how much water is in Jupiter,” he says. “But the answer to that question will help us understand how Earth got its oceans.”
Scientists theorize that Earth, which would have been initially dry due to its proximity to the sun, received its water supply from comets and asteroids. The intense gravity of Jupiter would have scattered comets and asteroids toward Earth; some of those objects would have collided with Jupiter, delivering water to it as well. Knowing how much water Jupiter possesses will help test theories of our own oceans’ origins.
“Water freezes out on the clouds of Jupiter, so we haven’t been able to measure it,” says Ingersoll. “The Galileo probe tried to measure water content, too, but it just happened to have been dropped into a particularly desert-like latitude.”
To determine the amount of water throughout Jupiter, Juno’s microwave radiometer will look about 300 miles below the clouds tops, where water vapor has not condensed out and is easier to detect. Jupiter’s radiation belts give off microwave signals that would interfere with the radiometer’s sensors, but because of Juno’s vantage point below the belts, the instrument will be able to capture spectral information on water that cannot be obtained otherwise.
Using data from additional instruments, Juno also should reveal more about the persistent jet streams and storms that roil the surface of Jupiter, such as the famous Great Red Spot. Discovering how deep the storms go could offer insight into why they can last for hundreds of years. “When you stir cream into coffee, it swirls together to form a lighter color,” Ingersoll says. “But on Jupiter, the storms don’t dissipate. We have some ideas about why this occurs, but questions persist.”
Caltech’s two other Juno team members are also eager to analyze the data Juno will collect. Dave Stevenson, Marvin L. Goldberger Professor of Planetary Science, leads the mission’s interiors working group, which will use information about Jupiter’s magnetic field and gravity to study wind motions below the surface as well as to determine the mass of the core and structure of the planet. Ed Stone, David Morrisroe Professor of Physics and vice provost for special projects, is the Juno senior advisor for science and management, a position he earned based on his more than four decades of experience as the Voyager project scientist. Stone is looking forward to learning more about Jupiter’s magnetosphere, which creates the planet’s brightly glowing auroras.
Juno’s instruments were turned off during the mission’s orbit-insertion maneuver through Jupiter’s radiation fields. The spacecraft now circles the planet in an elliptical orbit that safely avoids the radiation, so the instruments have been turned on. When Juno swings back around and passes closely over Jupiter on August 27, the instruments will be ready, and the world will get its first close-up look of the planet’s poles. “We’re ready for whatever Jupiter might throw at us,” says Ingersoll.
After nearly five years and 1.8 billion miles of space travel, NASA’s Juno mission will arrive at Jupiter on July 4, 2016. Managed by NASA’s Jet Propulsion Laboratory, the spacecraft will orbit Jupiter for 20 months, completing 37 orbits, and will then spiral down into the planet at the end of its mission in 2018. Three Caltech professors—Andrew Ingersoll, professor of planetary science; Dave Stevenson, Marvin L. Goldberger Professor of Planetary Science; and Ed Stone, David Morrisroe Professor of Physics and vice provost for special projects—are on the mission team. None are strangers to the giant planets—collectively, they have more than 100 years of experience studying the outer solar system. We spoke with them about Jupiter, the Juno mission, and the future of solar system exploration.
What is your specific role on the Juno mission?
Dave Stevenson: I lead the interiors working group, which has responsibility for interpreting the Juno data that tell us what is going on inside Jupiter: Does it have a core? What does the structure of Jupiter tell us about how it formed? Where is the magnetic field produced? How far down do the strong winds extend? The relevant measurements Juno makes are the gravity field, magnetic field, and water content.
Andrew Ingersoll: I am the head of the atmospheres working group and a member of two instrument teams—for the microwave radiometer (MWR) and the camera (JunoCam).
Ed Stone: I am a senior advisor for science and management.
What is special about Jupiter? What scientific questions are you hoping to answer with Juno?
DS: Jupiter makes up most of the planetary mass in our solar system. It probably formed before the other planets and controlled the architecture of our planetary system through its gravity. The way in which it formed will help us understand how planets in general form. And last but not least, it may even have controlled the delivery of water to Earth and thus affected the environment of our home planet.
AI: Jupiter is the largest planet and it comes closest to having the same proportion of chemical elements (hydrogen, helium, oxygen, carbon, nitrogen, sulfur, etcetera) as the sun. Also, it is like a fluid dynamics laboratory where storms last for decades and the planet’s rotation steers the winds into multiple jet streams.
With Juno, we would like to determine the average water abundance of the deep atmosphere. This question bears on the oxygen-to-hydrogen ratio on Jupiter compared to the ratio on the sun. The ratio is fundamental to how the elements were distributed through the early solar system and how Earth got its oceans. Additionally, we are trying to map how water and ammonia vary with latitude. This question bears on the weather below the visible clouds—a region we know little about. Jupiter has a very photogenic atmosphere, so we know a lot about the weather at the tops of the clouds. The unique phenomena there may derive their properties from the weather at deeper levels.
ES: Jupiter’s magnetosphere—the region occupied by Jupiter’s magnetic field—is the largest object in the solar system. Its radius is larger than the sun! The magnetic field is responsible for Jupiter’s aurorae—glowing regions in the north and south polar regions caused by ions and electrons spiraling down along the magnetic field lines. Juno’s orbit will be north-to-south, taking it over the poles and through the aurorae. We are interested in details about the aurorae—what kinds of particles are spiraling down into the atmosphere? What is the up-close structure of this huge magnetic field?
What other missions have you worked on? How do they compare?
DS: I’m also involved in Cassini, which has been spectacularly successful, especially for the satellites of Saturn, less so for Saturn itself. But in the coming year or so, Cassini will do some of the same things for Saturn that Juno will do for Jupiter by orbiting inside the rings and obtaining very precise gravity and magnetic-field data.
ES: I am the project scientist for Voyager 1 and Voyager 2, both of which conducted a flyby of Jupiter. They made videos of the winds, flew near the largest moons, determined the large-scale structure of the magnetosphere, and observed the aurorae from a distance. Juno is in a distinctly different orbit, and its electronics are protected from radiation so it can get closer to the planet. The Galileo mission was able to closely study the moons, but it was in an equatorial orbit. Juno is probing the inner frontier of the Jovian system and we expect many discoveries.
AI: I have worked on every mission to the giant planets—the Pioneers, Voyagers, Galileo, Cassini, and now Juno. I am amazed at the richness of the outer solar system. It seems that every time we go there with new instruments or visit a new part of it, we discover things that surprise us—things that our Earth-centric science couldn’t predict.
What is the future of giant planet exploration?
DS: Even though Cassini may be a success for Saturn, it will not answer one of the key questions that Juno should answer for Jupiter: How much water is there? For Saturn, that will probably require a probe—like the Galileo probe but going deeper into the atmosphere. A mission to an ice giant (Uranus or Neptune) is perhaps even more important and is high on the priority list for NASA. These kinds of planets are now known to be common in the universe and we know remarkably little about what goes on inside them.
AI: The immediate focus is on Jupiter and its moon Europa. The European Space Agency has the Jupiter Icy Moons Explorer (JUICE) and NASA has the Europa Orbiter. After that, Enceladus and Titan—two of Saturn’s moons—will be ripe for intensive exploration. The common theme is liquid water beneath the icy crusts of these outer planet satellites. With organic compounds and chemical energy sources, the icy moons extend the range of habitability outward from Earth orbit. That doesn’t mean they are inhabited, but means that many of the necessary conditions for life are present.
ES: The next major NASA mission will be to Jupiter and its moon Europa. We know from Galileo that there is a liquid water ocean beneath its icy crust. We know that on Earth, wherever there’s liquid water, there’s microbial life. Europa is certainly a place we want to explore.
JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for NASA’s Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. The California Institute of Technology in Pasadena, California, manages JPL for NASA.
Some of the wind-sculpted sand ripples on Mars are a type not seen on Earth, and their relationship to the thin Martian atmosphere today provides new clues about the history of Mars’ atmosphere.
The determination that these mid-size ripples are a distinct type resulted from observations by NASA’s Curiosity Mars rover. Six months ago, Curiosity made the first up-close study of active sand dunes anywhere other than Earth, at the “Bagnold Dunes” on the northwestern flank of Mars’ Mount Sharp.
“Earth and Mars both have big sand dunes and small sand ripples, but on Mars, there’s something in-between that we don’t have on Earth,” said Mathieu Lapotre, a graduate student at Caltech, Pasadena, California, and science-team collaborator for NASA’s Curiosity Mars rover mission. He is the lead author of a report about these mid-size ripples published in the July 1 issue of the journal Science.
On February 18, 2015, an explosion rattled the ExxonMobil refinery in Torrance, causing ground shaking equivalent to that of a magnitude-2.0 earthquake and blasting out an air pressure wave similar to a sonic boom.
Traveling at 343 meters per second—about the speed of sound—the air pressure wave reached a 52-story high-rise in downtown Los Angeles 66 seconds after the blast.
The building’s occupants probably did not notice a thing; the building shifted at most three-hundredths of a millimeter in response. But the building’s seismometers—one is installed on every floor, as well as on the basement levels—noted and recorded the motion of each individual floor.
Those sensors are part of the Community Seismic Network (CSN), a project launched at Caltech in 2011 to seed the Los Angeles area with relatively inexpensive seismometers aimed at providing a high level of detail of how an earthquake shakes the Southern California region, as well as how individual buildings respond. That level of detail has the potential to provide critical and immediate information about whether the building is structurally compromised in the wake of an earthquake, says Caltech’s Monica Kohler, research assistant professor in the Division of Engineering and Applied Science.
For example, if building inspectors know that inter-story drift—the displacement of each floor relative to the floors immediately below and above it—has exceeded certain limits based on the building’s size and construction, then it is a safe bet that the building has suffered damage in a quake. Alternately, if inspectors know that a building has experienced shaking well within its tolerances, it could potentially be reoccupied sooner—helping an earthquake-struck city to more quickly get back to normal.
“We want first responders, structural engineers, and facilities engineers to be able to make decisions based on what the data say,” says Kohler, the lead author of a paper detailing the high-rise’s response that recently appeared in the journal Earthquake Spectra.
The keys to the CSN’s success are affordability and ease of installation of its seismic detectors. Standard, high-quality seismic detectors can cost tens of thousands of dollars and need special vaults to house and protect them that can easily double the price. By contrast, the CSN detectors use $ 40 accelerometers and other off-the-shelf hardware, cost roughly $ 300 to build, and require minimal training to install. Approximately 700 of the devices have been installed so far, mostly in Los Angeles.
However, the CSN sensors are roughly 250 times less sensitive than their more expensive counterparts, which is why the ability to successfully detect and quantify the downtown building’s response to the ExxonMobil explosion was such an important proof-of-concept.
“It’s a validation of our approach,” says CSN’s project manager, Richard Guy.
Sonic booms have been noted by seismic networks dozens of times before, beginning in the 1980s with the first detections of seismic shaking caused by space-shuttle reentries. The sonic booms, found Hiroo Kanamori and colleagues at Caltech and the United States Geological Survey, rattled buildings that, in turn, shook the ground around them.
“Seismologists try to understand what is happening in the earth and how that affects buildings by looking at everything we see on seismograms,” says Kanamori, Caltech’s John E. and Hazel S. Smits Professor of Geophysics, Emeritus, and coauthor of the Earthquake Spectra paper. “In most cases, signals come from the interior of the earth, but nothing prevents us from studying signals from the air. Though rare, the signals from the air provide a new dimension in the field of seismology.”
The earlier sonic boom detections were made using single-channel devices, which typically record motion in one direction only. While this information is useful for understanding ground shaking, a three-dimensional record of the floor-by-floor motion of a building can reveal how much a building is rocking, swaying, and shifting; two or more sensors installed per floor can show the twisting of the structure.
“The more sensors you have in a small area, the more detail you’re going to see. If there are things happening on a small scale, you’ll never see it until you have sensors deployed on that scale,” Kohler says.
Kohler and her colleagues found that the air pressure wave from the explosion had about the same impact on the high-rise as an 8 mile-per-hour gust of wind. A pressure wave about 100 times larger would have been required to have broken windows in the building; a wave 1,000 times larger would have been necessary to cause significant damage to the building.
The ExxonMobil blast was not the first shaking recorded by the building’s seismometers. A number of earthquakes—including a magnitude-4.2 quake on January 4, 2015, with an epicenter in Castaic Lake, about 40 miles northwest of downtown Los Angeles—also were registered by the seismic detectors on nearly every floor of the building. But the refinery explosion-induced shaking was an important test of the sensitivity of the instruments, and of the ability of researchers to separate earthquake signals from other sources of shaking.
Other authors of the Earthquake Spectra paper, “Downtown Los Angeles 52-Story High-Rise and Free-Field Response to an Oil Refinery Explosion,” include Caltech’s Anthony Massari, Thomas Heaton, Egill Hauksson, Robert Clayton, Julian Bunn, and K. M. Chandy. Funding for the CSN came from the Gordon and Betty Moore Foundation, the Terrestrial Hazard Observation and Reporting Center at Caltech, and the Divisions of Geological and Planetary Sciences and Engineering and Applied Science at Caltech.