Source separation involves the ill-posed problem of retrieving a set of source signals that have been observed through a mixing operator. Solving this problem requires prior knowledge, which is commonly incorporated by imposing regularity conditions on the source signals, or implicitly learned through supervised or unsupervised methods from existing data. While data-driven methods have shown great promise in source separation, they often require large amounts of data, which rarely exists in planetary space missions. To address this challenge, we propose an unsupervised source separation scheme for domains with limited data access that involves solving an optimization problem in the wavelet scattering covariance representation space$\unicode{x2014}$an interpretable, low-dimensional representation of stationary processes. We present a real-data example in which we remove transient, thermally-induced microtilts$\unicode{x2014}$known as glitches$\unicode{x2014}$from data recorded by a seismometer during NASA's InSight mission on Mars. Thanks to the wavelet scattering covariances' ability to capture non-Gaussian properties of stochastic processes, we are able to separate glitches using only a few glitch-free data snippets.

Another Mars robot is settling in for a long, long sleep. With dust caking its solar panels, InSight has been losing the ability to recharge for months -- in the spring, it was operating at just one-tenth of its landing power. Now the thick layers of dust might have doomed InSight for good. NASA announced on December 19 that its InSight lander had not responded to communications from Earth, and "it's assumed InSight may have reached its end of operations." InSight, short for Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport, landed on Mars on November 26, 2018.

NASA's InSight lander has measured one of the biggest and longest marsquakes yet, which featured tremors of 4.2 magnitude lasting nearly an hour and a half, the space agency said. The robotic seismometre celebrated 1,000 days on the Red Planet on September 18, when it detected the largest tremor since it arrived at the Elysium Planitia in 2018. The 4.2 magnitude quake equals the largest detected so far on Mars, but on Earth that would be considered'light', with more than 10,000 earthquakes of that level detected every year, feeling like a light rumble that would make dishes shake. The lander was only able to make the measurement after efforts to clear dust from its solar panels earlier in the year - keeping the seismometre operating. The team took a counterintuitive approach to achieving this by sprinkling one solar panel with larger sand grains in the hope wind would blow it across the other panel and result in clearing enough of the dust to allow power to enter the device.

Data beamed back to Earth from NASA's InSight lander suggests Mars' crust is composed of three cake-like layers. Anchored near Mars' equator, the robotic lander's super-sensitive seismometer, known as SEIS, has recorded hundreds of'marsquakes' in the past two years. Each quake emits two sets of seismic waves and analyzing the differences in how those waves move has allowed researchers to begin calculating the size and composition of the planet's crust, mantle and core. 'We have enough data to start answering some of these big questions,' Jet Propulsion Laboratory scientist Bruce Banerdt told Nature. Launched in 2018, the InSight mission marks the first time scientists have peered inside a planet other than Earth.

Two years ago, NASA's InSight spacecraft alighted on the surface of Mars, aiming to glean clues to the planet's interior from the shaking of distant earthquakes and deep heat leaking from its soil. Mars, it turned out, had other ideas. Its sticky soil has thwarted InSight's heat probe, and in recent months howling winds have deafened its sensitive seismometers. Most mysteriously, the planet hasn't been rattled by the large marsquakes that could vividly illuminate its depths. Despite these hurdles, a precious clutch of small-but-clear quakes has enabled the InSight team to see hints of boundaries in the rock, tens and hundreds of kilometers below. They are clues to the planet's formation billions of years ago, when it was a hot ball of magma and heavier elements like iron sank to form a core, while lighter rocks rose up out of the mantle to form a capping lid of crust. The results, some debuting this month at an online meeting of the American Geophysical Union (AGU), show that the planet's crust is surprisingly thin, its mantle cooler than expected, and its large iron core still molten. The findings suggest that in its infancy, Mars efficiently shed heat—perhaps through a pattern of upwelling mantle rock and subducting crust similar to plate tectonics on Earth. “This may be evidence for a far more dynamic crust formation in Mars's early days,” says Stephen Mojzsis, a planetary scientist at the University of Colorado, Boulder, who is unaffiliated with the mission. The evidence has been hard won. Early in the mission, winds were quiet enough for InSight's seismometers, housed in a small dome placed on the surface, to hear a multitude of small quakes—nearly 500 in total. But since June, winds have shaken the surface strongly enough to smother all but a handful of new quakes. Yet frustratingly, the winds have not been strong enough to sweep away dust that is darkening the craft's solar panels and foreshadowing the mission's end sometime in the next few years. The seismometers are still running nonstop, but power constraints have forced the team to turn off a weather station when using the lander's robotic arm. “We are starting to feel the effects,” says Bruce Banerdt, InSight's principal investigator and a geophysicist at NASA's Jet Propulsion Laboratory. Meanwhile, the heat probe, about the length of a paper towel tube, is stuck in soil that compacted instead of crumbling as the rod tried to delve in. Mission engineers have used the robotic arm to push the probe down and scrape dirt on top. In the next month or two, they'll try once more to get the probe to burrow in, Banerdt says. “If that doesn't work, we'll call it a day and accept disappointment.” Perhaps the biggest disappointment is the lack of a marsquake larger than magnitude 4.5. The seismic waves of a large quake travel more deeply, reflecting off the core and mantle boundaries and even circling the planet on its surface. The multiple echoes of a large quake can enable just a single seismic station like InSight's to locate the quake's source. But above magnitude 4, Mars has been curiously silent—an apparent violation of the scaling laws that apply on Earth and the Moon, where 100 magnitude 3 events correspond to 10 magnitude 4 quakes, and so on. “That is a bit weird,” says Simon Stähler, a seismologist on the team from ETH Zurich. It could simply be that Mars's faults aren't big enough to sustain big strikes, or that its crust isn't brittle enough. But two moderate quakes, at magnitude 3.7 and 3.3, have been treasure troves for the mission. Traced to Cerberus Fossae, deep fissures in the crust 1600 kilometers east of the landing site that were suspected of being seismically active, the quakes sent a one-two punch of compressive pressure (P) waves, followed by sidewinding shear (S) waves, barreling toward the lander. Some of the waves were confined to the crust; others reflected off the top of the mantle. Offsets in the travel times of the P and S waves hint at the thickness of the crust and suggest distinct layers within it, Brigitte Knapmeyer-Endrun, a seismologist at the University of Cologne, said in an AGU presentation. The top layer may reflect material ground up in the planet's first billion years, a period of intense asteroid bombardment, says Steven Hauck, a planetary scientist at Case Western Reserve University. At 20 or 37 kilometers thick, depending on whether the reflections accurately trace the top of the mantle, the martian crust appears to be thinner than Earth's continental crust—a surprise. Researchers had thought that Mars, a smaller planet with less internal heat, would have built up a thicker crust, with heat escaping through limited conduction and bouts of volcanism. (Though Mars is volcanically dead today, giant volcanoes dot its surface.) A thin crust, however, might mean Mars was losing heat efficiently, recycling its early crust, rather than just building it up, perhaps through a rudimentary form of plate tectonics, Mojzsis says. A handful of distant quakes, originating some 4000 kilometers away, provided a further clue. Those waves traveled deep through the mantle and interacted with the mantle transition zone, a layer where pressure transforms the mineral olivine into wadsleyite. By analyzing the travel time of waves that passed above, below, and through the transition zone, the team located its depth—and found it shallower than expected, an indication of a cooler mantle. For the mantle to be this cool today suggests that convection—the swirling motions that, on Earth, drive tectonic plates and carry heat from the mantle to the surface—might have operated early on, says Quancheng Huang, a Ph.D. student at the University of Maryland, College Park, who presented some of the results at the AGU meeting. “Plate tectonics is a very effective way of cooling a planet.” A third science experiment aboard InSight probes deeper still, using tiny Doppler shifts in radio broadcasts sent from Earth to receivers on the probe to detect slight wobbles in the planet's spin. The size and consistency of the planet's iron core affect the wobbles, much as raw eggs spin differently from cooked ones. “We've had something like 350 hours of tracking,” says Véronique Dehant, a geophysicist at the Royal Observatory of Belgium. The preliminary results confirm that the core is liquid, with a radius compatible with previous estimates made by spacecraft measuring tiny variations in the planet's gravity, Dehant reports in her AGU poster. Those gravity estimates have found a core with a radius of about 1800 kilometers—taking up more than half the planet's diameter. Rebecca Fischer, a mineral physicist and modeler at Harvard University, isn't surprised at the signs of a liquid core. “It would be a pretty big surprise if it weren't,” she says. Sulfur and other elements mixed with the iron should help it to remain molten while cool, much as salt prevents icing. On Earth, convective motions in the molten outer core drive the magnetic dynamo. But on Mars, those motions seem to have stopped long ago—and without a magnetic field, the planet's atmosphere was vulnerable to the Sun's cosmic rays and leached water to space. Banerdt hopes to sharpen this fuzzy picture of the planet's interior, and he thinks calmer winds will soon make that possible. After two Earth years, the probe's first martian year is ending, and the quiet of the mission's first months is returning. “We're looking forward to another whole pile of event detections,” Banerdt says. And though the planet has not cooperated so far, perhaps the Big One is poised to strike Mars like a gong—a reverberation that would at last make all clear.

It is notoriously hard to build a bad Random Forest (RF). Concurrently, RF is perhaps the only standard ML algorithm that blatantly overfits in-sample without any consequence out-of-sample. Standard arguments cannot rationalize this paradox. I propose a new explanation: bootstrap aggregation and model perturbation as implemented by RF automatically prune a (latent) true underlying tree. More generally, there is no need to tune the stopping point of a properly randomized ensemble of greedily optimized base learners. Thus, Boosting and MARS are eligible for automatic (implicit) tuning. I empirically demonstrate the property, with simulated and real data, by reporting that these new completely overfitting ensembles yield an out-of-sample performance equivalent to that of their tuned counterparts -- or better.

The American space agency's InSight lander appears to have detected its first seismic event on Mars. The faint rumble was picked up by the probe's sensors on 6 April - the 128th Martian day, or sol, of the mission. It is the first seismic signal detected on the surface of a planetary body other than the Earth and its Moon. Scientists say the source for this "Marsquake" could either be movement in a crack inside the planet or the shaking from a meteorite impact. Nasa's InSight probe touched down on the Red Planet in November last year. It aims to identify multiple quakes, to help build a clearer picture of Mars' interior structure.

It sounds like a subway train rushing by. But it's something much more exotic: in all likelihood, the first "marsquake" ever recorded by humans. NASA's InSight mission detected the quake on April 6, four months after the lander's highly sensitive seismometer was installed on the Martian surface. The instrument had previously registered the howling winds of the red planet and the motions of the lander's robotic arm. But the shaking picked up this month is believed to be the first quake from Mars' interior.

NASA's InSight lander is leaning in for a better listen of Mars' underground tremors. The robotic explorer placed its seismometer on the surface at the end of last month, and is now getting even closer'for a better connection with Mars.' This will help its instruments pick up fainter signals that may otherwise have been missed. NASA's InSight lander is leaning in for a better listen of Mars' underground tremors. The robotic explorer placed its seismometer on the surface at the end of last month, and is now getting even closer'for a better connection with Mars.' Before and after images show its instrument at its lowest position yet Days prior, InSight leveled out its seismometer and adjusted the internal sensors ahead of lowering everything down toward the ground.

NASA's InSight lander has deployed its first instrument onto the surface of Mars. New images from the lander show the seismometer on the ground, after it was lifted onto the surface by the lander's robotic arm. It will record the waves traveling through the interior structure of the planet, and could help explain mysterious'marsquakes' scientists believe occur regularly. New images from the lander show the seismometer on the ground, after it was lifted onto the surface by the lander's robotic arm. It will record the waves traveling through the interior structure of the planet, and could help explain mysterious'marsquakes' scientists believe occur regularly.