Thanks to geodesic studies into the way Mars wobbles (nutation - feel free to send questions if you want to know more about this), it seems like NASA’s figured out that Mars actually has a liquid core! This is exciting but how on Mars could we possibly learn more?
Seismology.
On Earth, most earthquakes are the result of tectonic plates moving around. They are a physical manifestation of the internal planetary energy seeking a way out. On Mars there are no tectonic plates. This is a fascinating and broad subject within planetary geology but the fact doesn’t mean Mars is without its own seismic activity: volcanoes also produce quakes.
On Earth, seismic activity around volcanoes can be seen as a precursor to volcanic activity. Interestingly enough, this could also be true on our red neighbor:
(Image credit: E. Hauber, P. Brozˆz, F. Jagert, P. Jodlowski, T. Platz, Very recent and wide-spread basaltic volcanism on Mars, Geophys. Res. Lett. 38, L10201 (2011))
The dark green dots on the image above indicate what Hauber et al. (2011) believe to be very new terrain on Mars. Less than 100 million years old. If both this and NASA’s conclusion regarding a fluid interior are true: Mars may not have erupted its last yet. Both of these things would seem to indicate a current stockpile of internal energy.
What’s more? Methane has been detected numerous times. Since methane breaks down very quickly, this means there is something on Mars currently producing methane. It’s probably worth noting that one way it’s created (geologically) is when underground water mixes with olivine rock. It can then emerge from volcanic activity.
In a few months NASA will be launching the InSight mission. The landing zone is Elysium Planitia, an extensive volcanic region.
It’s possible when NASA takes the Red Planet’s pulse, they will find a planet full of geological life. If so, this could also indicate a powerful way to investigate the interior of the planet in the future. In the plots I made at the top you can see Earth and Mars next to each other. I tried to scale them relative to each other. On Mars you can see that we have an idea of what’s under the crust, but until we actually go and start detecting seismic activity, we won’t know.
Who cares you say? Well you should: if Mars is still geologically active it could shed light on why Mars lost its magnetic field, (most of) its atmosphere, any oceans it may have had and therefore its potential habitability. Furthermore, learning these things will give us a powerful new way of thinking about terrestrial planets, how they evolve and what it might be like on other worlds far from us in other star systems.
Remember that scene from Prometheus where the two flying probes are sent into the halls, laser scanners flashing every which way?
That’s a real thing now… well sort of.
The European Space Agency has a program called PANGAEA which is aimed at developing geology training programs for astronauts. As a part of this program a new technology was recently deployed and tested in Spain’s extensive La Cueva de Los Verdes lava tube. It’s actually a pair of technolpogies called the “Prgasus Backpack” and the “Leica BLK360″.
The Pegasus Backpack is a wearable “3D mapper”. This is something that could be used to map out street views similar to the Google Street View. What makes it so cool though is that the backpack doesn’t require a satellite connection, enabling it for use inside places with poor connectivity.
The Leica BLK360 is a LIDAR camera (Laser Imaging, Detection and Ranging). What LIDAR does is it shoots out a beam of laser light and thanks to the speed of light, is able to get an extremely accurate measurement of the distance from the camera the laser beam hit something and bounced back to the LIDAR camera. The camera detects this bounce back and does it again many more times, putting together a scan of the surrounding space: essentially an image of the room you’re in (or for many spacecraft, of the topographic features of the planetary surface below it).
When combined, as researchers with PANGAEA did, they were able to go deep inside the La Cueva de Los Verdes lava tube, away from both satellite connections and light, and create a detailed, 3D map of the entire lava tube.
Here is a fly through:
(The lava tube has a total length of about 8 km and detail goes all the way down to a few centimeters in resolution)
Why is this important? As exploration of the Solar System continues on places like the Moon and Mars (Venus too if I could have my way), we find evidence of dynamic geologies that could take research below the ground. The Moon, Mars and Venus all have lava tubes. This new method could enable detailed exploration of subsurface locations on many of these worlds like how they formed.
It’s also worth noting that if something like a lunar base were ever created, the lava tubes on the Moon would present a stable, radiation-protected region that could be used to house astronauts.
(Image & video credit: Vigea – Tommaso Santagata and ESA respectively)
I'm an aspiring undergraduate astronomer, but I'm graduating next year and I'm not sure what to do for graduate school. I think I want to do work with the interstellar medium. Which schools would you recommend applying to?
Hello! So I focus on planetary science which is almost as far as you can get from ISM research. That said I know there’s a good amount of ISM stuff at all of the big names like Caltech, MIT, etc.
More than simply applying to schools however, I’d recommend you look for specific professors you’d like to work with and reach out to them. Having personal connections is really effective for getting into graduate programs - it would be beneficial to you for finding a research adviser you get along with (and vice versa!). I hope this was some help and good luck!
(An unedited reflection on science and my time studying it)
The value of Mars exploration is great,
but perhaps also elusive. The “red planet” holds 4-billion years
of geological history to explore, the surface of which is yet to be
scratched. In order to appreciate the value of exploring Mars
however, you need somewhat of a historical perspective. Some of the
most groundbreaking advances in technology (and therefore quality of
life) were not the result of
predetermined intent. Almost every discovery made, has been a
surprise. Therefore the value of exploring Mars, is in its own right
a mystery. This question can be approached in terms of potential; It
is entirely obvious that a place as large and old as Mars has an
intriguing set of clues to fundamentally important questions: why do
planets evolve differently from the Earth, how did Mars lose its
atmosphere, was there ever running water on the surface of Mars, and
are we alone? So in a sense we can assign value to exploring Mars
based on the questions we intend to explicitly explore. Even this
won’t do full justice to the actual value that would come from
exploring Mars, for this
assumes that we know what questions to ask. The safest way to
appreciate the significance of exploring this place is to look back
and see how scientific exploration has always turned out.
It is
somewhat ironic that in order to justify science, historical evidence
needs to be recalled. The
nature of scientific inquiry is most often serendipitous. For
example, when Isaac Newton sought to explain how it was that planets
moved throughout the Solar System, he invented calculus. In doing
this Newton almost certainly didn’t expect to also invent a branch
of mathematics that empowered humanity to create computers, robotics,
and even fly supersonic jets across the sky. Yet in a sense, these
are all distant relatives of astronomy thanks to their common origin
in calculus. This example, although dramatic, has a thread of truth
that runs through the entire history of science. Even in cases of
profound theoretical prediction, like the prediction of the Higgs
Boson, discovery is still inevitable
both in the sense that a theory is never complete in its prediction,
but also in the sense that scientific consensus will not be reached
until after a discovery and so this still represents a collective
epiphany.
The
value of exploring Mars is just the next piece in this thread of
serendipitous adventure. Qualifying this exploration on the word
“why” radically devalues the magnitude of our ignorance of that
world, and of the amount of exploration it would require to “conquer”
it; For to explore Mars, we must explore our own potential in ways
that have never been done before. We have to explore the ways space affects us biologically, we need to explore our potential
to look at what is currently impossible, and engineer the
impossibility away. Martian exploration provides us with so many
challenges that the value of the exploration is only partially
about the planet itself. Is the point of weightlifting to make a
heavy object inhabit space a few feet higher than before? The value
of exploring Mars is obviously encompassed in all the mystery hidden away in the 4-billion year history of the Red
Planet, but there is more: the value of exploring Mars is in all the ways it’s currently difficult, and how those things no
longer will be afterwords. In a sense, a post-Mars humanity will have grown
in all the
ways where now Mars exploration challenges us (i.e. a lot). Exploring
Mars, means radically empowering humanity. It is important to
therefore look at where problems arise that make Martian exploration
difficult, for the solving of such problems is therefore the minimum
boundary on the value of exploring Mars.
By
defining the values of such work in this way, we inevitably draw our
appreciation for the benefits in terms of what the costs are. Space
exploration in this sense is an investment in ourselves. So therefore
in order to really narrow down how to value the exploration of Mars,
we need to first explore how this endeavor is costly. There are
obviously many ways in which something like this is expensive, most not defined explicitly in terms of financial cost;
For example: there could be physical costs, political costs, and even
spiritual costs etc. Finally it is critical to understand that just
as the true values of science are often serendipitous in nature, so
too can the costs be unexpected. Therefore the following suggestions
are meant as the minimum
ways in which such a voyage may cost humanity.
It
makes sense to begin with the most obvious way in which a voyage to
Mars will cost us: financially. A trip to Mars in any aspect will
incur exorbitant expenditure on behalf of the peoples and governments
sponsoring such a voyage. A common
saying
is that for every pound launched into orbit it costs “$10,000”.
This may not be exactly
accurate but it captures the point. Every
aspect of space exploration is tremendously costly and this begins
with the fact that to even get to space, massive amounts of money
need to be put into a launch vehicle. This is true for Mars too. There are numerous ways to make the journey, whether by a
Cycler orbit, a Hohmann Transfer or through some other method not yet
clear to us. For each, here will be a cost. For example, in order to get to Mars
by using a Hohmann Transfer you need enough fuel to not simply get
your astronauts and supplies into space, but to stretch your
orbital trajectory so that it goes from Earth to Mars where you then use more fuel to slow down. The amount of fuel
to do this is tremendous. Furthermore, since this method means simply
orbiting your way into a Martian gravity well, you are only going to
move so fast. Therefore a crew must be able to survive in space for
that long. When you think about how every pound launched into orbit
is that much more of an expense, and how much food you eat in a few
months: it’s obvious as to why the cost rises quickly.
So
obvious is it that a voyage to the Red Planet would cost a lot of
money, that the case hardly needs to be made. Focus therefore should
be on the ways that costs could surprise us. For
example, if there are long-term consequences of being in microgravity
for extended lengths of time we aren’t yet aware of. This is
something that we may have figured out but until the experiment is
actually done, we just won’t know for sure. Furthermore, it is
clear that if something were to go wrong and lives were lost because
of this mission(s), politicians could easily face consequences. Just
like war efforts, grand explorations missions may be tied to the
identity of a single politician
for whatever reason. This was obviously the case with President John
F. Kennedy thanks to his “We will go to the Moon” speech. If
something were to go wrong then a highly visible exploration effort
could become a prime target for political fodder. The Apollo missions
are generally regarded as success stories but even so when Kennedy’s
old political opponent Richard Nixon ascended to the Presidency, NASA
found itself ordered to dismantle the Apollo missions and begin
focusing on the construction of the Space Shuttle – often regarded
as a retreat from NASA’s ambitious
human missions.
Due
to the volatile nature of
politics, NASA may be forced
to change their approach
halfway through a directive:
should we go straight to Mars or should we go to the Moon first? One
administration may want one thing and another a different one. This
constant changing of direction could not only force NASA to spend
money on things that have already been accomplished in different
ways, but it could repeatedly drive away potential contract bidders. Less options will almost certainly result in not having
the most favorable option at least once, and therefore drive up
costs. A private contractor cannot be expected to always bear the brunt of
political misfortunes on
behalf of a government agency.
This
potential for these costs
to be unexpectedly driven up is representative of the risks taken by
the private sector. When a
contract is set to outlast an officeholder the contractor is taking a
gamble that the next officeholder will continue honoring said
contract. The risks of space missions paying off are therefore
economically uncertain. Since budgets are points of
intense debate (and partisanship) in Congress, whether or not a
company will get paid on time (or at all) depends on the year.
The relationship extends to taxpayers: NASA missions have historically
contributed wonderful spinoff technologies that have helped drive the
economy and society overall.
The
space program for example, has contributed many cornerstone
advancements of the modern world: whether it’s communications
satellites, CATScan technology or
smoke detectors. Without a doubt the world would be a dramatically
different place today if it weren’t for these things. Hindsight makes it clear the scientific investments that led to such technological achievements were wise
ones. It should be emphasized that this payoff wasn’t and still
isn’t clear beforehand. Many such advancements however were the result of risks that astronauts
faced on their missions led to humanity radically pushing its
boundaries to specifically find solutions for those astronauts.
With
this in mind it’s clear that there is a duality to the
risk-payoff nature of a mission to Mars. Like previous
astronauts, Martian explorers would face a list of known risks (and
likely numerous unclear ones). It will take tremendous effort on the
part of scientists and engineers to solve the numerous problems
people would face on their way to Mars, but if these problems are
solved, the technical payoff would reverberate back to Earth. This is
an inevitable benefit of the space program. Simply
by understanding the physical risks inherent to astronauts it’s
possible to begin inferring the sorts of benefit Earth would reap by
their solving; For example one solution being worked on at the EVA
laboratory at MIT is the BioSuit.
This suit utilizes a system of small springs built into the suit to
provide pressure to the body, rather than an astronaut suiting up
inside a balloon. Professor (and previous Deputy Administrator of
NASA) Dava Newman is working on this concept. She says that there is
potential for such a spacesuit to help both
victims of cerebral palsy and strokes:
“We
have been working with colleagues at Children’s Hospital in Boston,
Harvard’s Wyss Institute, Boston University, and Draper Laboratory
to see if we can use our technology and engineering designs to help
infants with brain damage that affects motor skills, children with
cerebral palsy, and stroke victims, who typically lose motor skills
on one side of their bodies. The idea is first to use BioSuit
“sleeves” with builtin sensors on the legs to measure
movements—to understand, for instance, how much motion and kicking
by infants is typical and compare that with the limited kicking and
motions of children with cerebral palsy. The next step—a big one—is
to add actuators that can enhance and direct movement. In the case of
cerebral palsy and stroke victims, that would be a way of giving back
some of the lost motion. People with cerebral palsy expend a lot of
energy moving and have stiffened muscles; our BioSuit technology and
know-how could guide movement and enhance mobility to make it more
efficient. And because the brains of newborns are still so plastic,
enhancing the natural kicking of infants with potential motor
problems from brain damage might actually reshape the motor programs
and partly “heal” their brains.”1
If true, it’s clear that there is
incredible potential to help humans on Earth, even in the minutia of
a mission to Mars. Although astronauts face personal risks on such
missions, the risks of not undertaking missions like this in general
span all of humanity. To not
go to Mars is therefore a planetary risk, though it’s not
explicitly clear how, and to what magnitude. If it were clear this
would probably be a somewhat more common justification. To not go to Mars
is to stunt human potential, especially in the intersection of
biology and technology: a place where further understanding and
capability have great potential to change lives.
It is therefore difficult to divorce
the idea of sending astronauts to Mars from the risk of becoming
uninvested in relevant scientific exploration. Space exploration is
inspiring and motivating. Extraordinary efforts go into advancing
space science and it requires such extraordinary efforts. Rare is it
that such difficult problems attract swaths of young minds to the
STEM fields. Space exploration however, is one such rallying point –
perhaps the best. On several levels this is relevant: students who go
work in space exploration that contributes civilization-wide
spinoffs, students who go into STEM intending to work in space
exploration (but maybe end up somewhere else), and students inspired
by space exploration but don’t end up in the STEM fields. The first
two groups contribute to the global infrastructure, technology and
economy directly: one from whatever spinoffs result in the space
program and the other by working directly on terrestrially-sourced
problems. The third group may not directly contribute to technical
achievements but would almost certainly provide the political support
NASA and various science agencies need in order to attract public
funding. This is all due to the technical and economic feedback loop
that exciting exploration programs like a mission to Mars would
result in. Were we to not go
to Mars, this feedback loop would obviously shrink or die to some extent. This is a risk of not exploring Mars.
Considering
all the different ways in which risks and benefits are intimately
tied in space exploration, we can assume
that by facing the risks of a mission to Mars, we stand to gain quite
a lot. Nevertheless it is impossible to know exactly what benefits
would come of it. Societies have never faced civilization-wide
detriment for indulging the spirit of exploration (to my knowledge), however. It’s
important to then really face the idea of whether or not a mission to
Mars is truly justified. It will certainly take a lot of money and a
lot of physical risk on the part of the astronauts. Fundamentally
these are the prohibitive risks. Perhaps it would be useful in light of the benefits of scientific exploration to frame the question as “what are the risks of not exploring Mars?”
On the other hand greater risks are
taken with far less scrutiny: is invading another country a risk?
It’s almost certainly going to cost more money, more lives and have
far more geopolitically divisive consequences than a mission to Mars.
Realistically, there are many activities conducted by or on the
behalf of governments and nations that incur damage to economies and
lives than space exploration. Space exploration is one of the few
things that can be done that will almost certainly benefit the global
economy, infrastructure, quality of life, and unite disparate
political groups. The risks are almost inscrutably small to the
average person. The only consequential dangers are to the astronauts
on the mission – and these people are almost unanimously hailed as
heroes as they voluntarily put humanities best foot forward into the
dark, bringing enlightenment back to us. It is clear that Martian
exploration is justified.
This
is a common perspective across the fields of science (though maybe not unanimous). The issue of
whether or not space exploration is justified (and specifically a
mission to Mars) seems to be more controversial to the “uninitiated”
in the STEM fields. Assuming this to be true, it isn’t clear to me
why. It could be true by definition if such people were in part
brought into the Stem “fold” by being inspired by things like
space exploration (being a part of that “feedback loop” mentioned
above) or science fiction. Like
parents, scientists often dote on their research, yet a new parent is hardly ever
asked “what is a newborn baby good for?”.
Before
starting my astronomy degree, I was a humanities student.
Although intrigued and supportive of the space program, I approached
problems in fundamentally different ways. I would ask “What’s
possible?” in the context of modern technology. As a scientist
(sort of) I find myself asking questions more akin to “How can this
be made possible?”. I don’t know exactly
why this perspective shift happened but it certainly
occurred
(probably gradually). As a
longtime lover of science fiction, my core sympathies and hopes were
always in entirely in favor of the space program. The change in
perspective as I see it, is probably more fundamental. Among the
scientists I’ve spoken to, if going to Mars were entirely up to
then it would be only a question of how to make it happen. Science is
fundamentally explorative in nature. Having trained my mind to
rigorously indulge intellectual curiosity over the last four years
has possibly promoted shift in perspective. After studying astronomy
and physics I can now acknowledge that I do see the world differently
than before. The mysteries are different, and mystery itself means
something different. Mystery is no longer a wrench in the machine of
the world, a source of impossibility, ignorance or magic.
Mystery is now a target, a destination – the
magic, in a sense, is still there. It is no longer the superstitious
fear of walking a minefield but the magic of opening a gift,
traveling to a new place, and in doing so uniting the universe I see
with the internal growth from knowledge and experience.
(Top image credit: NASA
Image & quote source: Newman,
D. (n.d.). Building the Future Spacesuit. Ask
Magazine.)
Did you know the government of New Mexico still considers Pluto to be a planet? In fact March 13th is “Pluto Planet Day”! So mark your calendars, it’s coming up.
On Earth the atmosphere accounts for roughly 1/1,000,000th of the mass of the planet (i.e. not much at all). On Jupiter however, it’s a different story.
The horizontal bands that cross Jupiter have long been known to be giant jet streams with forces going up to 100 times that of any hurricane on Earth. How similar are these atmospheric forces to those found on Earth? It turns out, probably pretty different.
Researchers from NASA’s Juno mission team (led by Professor Yohai Kaspi) have found that the gravity measurements from their spacecraft indicated a strangely deformed gravity field. In fact, they found that about 1% of Jupiter’s mass is in its extensive atmosphere. This means that a gravitationally detectable amount of mass is moving in these currents. The bands (which are visible with an 8″ or so telescope!) on Jupiter actually extend as far as 3,000 km below the surface. Impressive.
I admit to writing a rather “clickbaity” name for this post but who’s to say, perhaps some daring planetary scientists will try to come up with a system of weather forecasting based on gravitational anomalies? The future is now!
There’s been quite a lot of debate going on regarding how exactly the Moon formed: most seem to agree that when a Mars-sized planetary object struck the Earth, somehow the debris thrown into space formed into the Moon.
There’s actually quite a bit of evidence this is true: chief of which are the similarities in isotopic ratios of various elements found in Apollo samples and terrestrial rocks. We don’t, however, have a good idea of what the chaotic Moon-formation time looked like. Researchers from Harvard (and UC Davis) have just proposed a new theoretical object, called a “synestia”.
The synestia would look “donut-like” in shape (as shown above). It would be made of rocky materials liquefied during a planetary collision. How does this work?
An impact injects kinetic energy into a planetary body, increasing the planet’s temperature. If you think of this on a molecular level, the molecules are beginning to move faster.
Now, zooming back out, think about how a planet rotates: because this rotation is axial, an equator needs to be moving faster than the poles for the surface to be continuous.
Now lets put those two things together: The material of the planet is moving faster due to an increased temperature, and the equatorial material is moving even faster.
Bingo. The velocity of the liquefied material at the equator, it turns out, actually begins to intersect with the velocity required of a basic Keplerian orbit!
This is a controversial problem with more traditional approaches to Moon-formation theories where most impact scenarios actually imply that there isn’t enough energy for debris to reach orbit around the Earth.
It’s from these synestias that it’s thought things like the Moon may have formed out of.
According to a model built by researchers Simon Lock and Professor Sarah Stewart, these objects exist during planetary collisions and can be potentially seen by astronomers. Synestias could potentially explain the great diversity of ring and satellite systems that exist: from the Moon the the lopsided rings of Neptune. This research is both promising and extremely exciting!
As the search for habitable worlds continues, it is worth considering what habitable means. In recent decades the Goldilocks Zone concept, regions around stars where planets can sustain liquid water, has been the main method of honing in on potentially habitable worlds. However this constraint might be too narrow: moons in the Solar System like Europa, Enceladus and Titan provide exciting new possibilities for habitability. These worlds offer evidence that researchers may need to adjust their priorities if they are to advance the search for habitable worlds. Key clues regarding where to direct such a search might lie in the detection and exploration of new exoplanetary ring systems. If this is the case, the search for habitable worlds has yet to begin benefiting from the most productive class of objects, exomoons.
Consider the transit in the case of an exoplanetary ring system: as long as there is some tilt with respect to the plane of the rings and the transit plane, such rings may give off telltale signs of their existence. At first glance it might seem likely that the transit signal of an exoplanetary ring system would have equal “ring” transits on either side of the actual planetary transit. Not so: such ring systems may actually be tilted with respect to both its axis of orbit and with respect to us. If so, this produces an asymmetry in the light curve:
Figure 1: The above image matches potential ring astrometry (i.e. positions) with transit curve variations below. (Image credit: Kenworthy, M. A., & Mamajek, E. E. 2015, ApJ, 800, 126)
In the search for extrasolar rings and moons there are two crucial parameters necessary to improve: astrometry and photometry. Astrometry is the precise measurement of the positions of celestial bodies while photometry is the precise measurement of light (how much a target is emitting or reflecting). Because the signal changes due to exoplanets are often so small, these two parameters must be as exceptional as possible. Effects like atmospheric turbulence and even light from both the Moon and the sun have historically presented challenges to exoplanet hunters. Since the targets only have small signals, it takes only a small effect (like a humid day) to add lots of noise into a signal. In a case where there is a low signal-to-noise ratio, how much more signal is from the target compared to the typical noise, certainty in alleged detections drops rapidly. The transit of 1SWASP J140747.93-394542.6 (hereafter referred to as J1407) presents researchers with what might be the first discovery of extrasolar planetary rings: photometric measurements show a stellar drop in magnitude of roughly 95% during transits. As Mamajek argues in a 2012 paper, these measurements are excellent matches to potential ring systems. Mamajek shows that an extensive ring system, some 90 million km.
It is crucial to raise confidence in these conclusions by observing such transits again around both J1407 and other planets. If we are limited by our astrometric and photometric abilities then it makes sense that the first significant ring system discovery may have been a massive ring system. With our technical capabilities still in infancy, only the easiest such ring systems are detectable. Since other phenomena could potentially fit the data, there is still work to do before Mamajek’s discovery can be confirmed. An important consideration to make here is that most planets with ring systems will be locally dominant in their gravitational fields: this means there is a limit to how close it can be expected that a ringed-exoplanet is to its host star. Consider now Keplerian dynamics: the farther away such an object is, the larger the period of orbit. This leaves few options for confirming exoplanetary ring systems other than one-off transits, then confirmed by other means. The radial velocity method would be a may be a productive way to confirm the presence of such an orbiting body. Given that this transit has a length of 54 days (and is from a ground-based telescope), there are 54 gaps in the data. This can lead to difficulty in constraining the signal. Without care it can be easy to misinterpret a transit like this when there are numerous alternative explanations.
False alarms may otherwise be indistinguishable from exoplanetary ring signals. Collections of debris could produce similar patterns in transit signals. Because ring systems are typically expected to have large periods around a host star, it would be extremely challenging to distinguish between ring systems and debris fields. Furthermore, Trojan groups of asteroids, like the ones that precede and follow Jupiter in its orbit, may provide some similar pattern variations, although large photometric signals like the ones detected around J1407 (95% drop in magnitude) would have to be from Trojan bodies significantly larger or more populous than those found near Jupiter.
Starspots are also important considerations. When an object transits in front of a star spot it will briefly block less light than it otherwise would have; This leads to a slight brightening during a transit. Luckily, multi-band measurements can identify starspots since they are functions of wavelength. Variations in orbital and rotational periods also allow researchers to distinguish between transit events and star spots.
Being able to reliably distinguish between the transit of a system of rings and other events is critical in the search for exomoons. It is worth consideration that ring structures and exomoons are not mutually exclusive. In our own Solar System the most notable collections of moons are around gas giants, all of which have ring systems. Kenworthy et al. note that the ring system around J1407 has varying “transmission” levels: light from the host star passes through various parts of the ring structure in various amounts depending on the object’s orbit.2 The authors interpret this to mean that there are gaps in the structure, allowing them to give a lower limit on the number of expected rings. The authors speculate that if this assessment is correct, it could be the first evidence of exomoons sculpting the ring systems of an exoplanet. This has direct analogues in the Solar System where moons like Titan and Enceladus have dynamic relationships with the rings of Saturn.
This evidence is far from conclusive, however. As mentioned before, improvements in astrometry (particularly spectroastrometry) may be where researchers need to focus improvements in order to make exomoons detectable. Spectroastrometry is the combination of spectral analysis with astrometry. In order to fully break down what this technique is, we must explore the component constraints: telescope size, spectral resolution, the signal-to-noise ratio and the ability to block light - most likely by virtue of a coronograph. By having a telescope of enough size astronomers are able to get the required spatial resolution to image an exomoon. If there is an Earth-Moon twin system at Alpha Centauri for example, a telescope with spatial resolution of 5.55x10-7 degrees would be able to see the planet and moon as being two distinct objects. A 12-meter space telescope (like the proposed “High-Definition Space Telescope”) would be able to observe such phenomena. Spectral resolution is a matter of instrumentation, this constraint is solvable yet important to remember. It’s simply the smallest detectable change in the electromagnetic spectrum (the light spectrum). This allows confidence in small measurements, unhindered by fear of noise in the data. Finally, with an object like a coronograph or starshade, the host star’s light can be blocked out. Without that this entire endeavor would be almost impossible.
With all of these concepts put together, the spectrum that would be expected in an Earth-Moon analogue would be like this:
Figure 2: Top image shows the flux density of the Earth and Moon analogues. The bottom shows the percentage of flux density the Moon is responsible for. (Image credit: Agol, E., Jansen, T., Lacy, B., Robinson, T. D., & Meadows, V. 2015, The Astrophysical Journal, 812, 5)
The top image shows the spectrum of light detected from the Earth in blue and the spectrum of the Moon in gray. Notice how for Earth the H2O region dips down? This is because Earth has water on the surface that absorbs that light. The Moon, therefore will reflect more of the H2O portion of the light than the Earth, i.e. the Moon becomes brighter in that particular portion of the spectrum. The bottom image shows the percentage of the spectrum that the Moon contributes (as a function of wavelength). The horizontal dotted line indicates the percentage below which the spectra is dominated by Earth-light.
With refined spectroastrometric capabilities, the hunt for habitable worlds will vastly expand. In the Solar System, numerous ocean worlds are known to exist: the Earth being the only one in the “Goldilocks Zone” of the sun. Enceladus, Europa, Pluto, etc. all may contain vast reservoirs of liquid water (and Titan has an ocean of liquid methane!). It is only a recent revelation that life as we know it needs no sunlight to survive. Deep in the ocean there are hydrothermal vents which provide the chemical energy needed to sustain subsurface life. No photosynthesis exists. In so many of these ocean worlds, specifically Enceladus and Europa, their giant host planets are pumping them with tidal energy, heating their interior and potentially enabling extraterrestrial genesis. Such a discovery would require immense evidence to convince researchers, and it’s possible that the more fruitful targets are not terrestrial exoplanets but exomoons.
Volcanoes, magnetic fields, “marsquakes”, and planet formation: how do all of these things tie together? From studying exoplanets to understanding the difference between Earth, Venus and Mars, a significant amount of insight resides on the inner pulses of a given planet.
Here on Earth these things are often studied by virtue of seismic data. the way earthquakes propagate throughout the planet allow geophysicists to study the interior of the Earth. Since many of the problems fundamental to planetary formation and habitability depend on things that are going on inside a planet, it seems natural that we might wonder at our extraterrestrial neighbors.
Enter InSight: NASA’s next Mars lander. On this spacecraft there will be a seismometer called SEIS which will detect quakes that travel across the inside of Mars, potentially revealing details of what’s inside. It has long been thought that the core of Mars has cooled down, giving us an explanation as to the absence of a magnetic field.
Since seismic energy travels in several forms (primary waves, secondary waves and surface waves) it’s worth a brief overview of what these waves are. On Earth, P-waves (”P” for primary of course) are waves that oscillate like so:
A critical distinction between these two waves is that only P-waves can propagate through a fluid. That means that if you are detecting a tremor in a planet that is only giving you P-waves, there is a fluid layer blocking the propagation of the S-waves. Surface waves are not so important for the study of a planet’s interior (did this need to be said?).
How exciting would it be if an S-wave shadow zone were discovered on Mars? It would certainly open extensive debate not only on Martian history but could also have ramifications for terrestrial exoplanets and what we think we know about them.
We don’t actually need such a shadow zone to get valuable information on the Martian interior however. Not only do P-waves travel faster than S-waves, but both waves also reflect and refract seismic energy in predictable manners as they travel across the bounds of different layers in a planet. InSight and the SEIS experiment are very likely to provide some incredible new information to the planetary community.
The astute reader may have noted by now that if the planetary core is solid, Mars may not actually be doing much quaking for SEIS to detect. Good catch! Researchers have a wonderful solution: let the universe smack it back to life! Here on Earth the detonation of nuclear bombs give seismologists a way to artificially produce seismic energy, but on Mars the lack of an atmosphere means that a significant number of meteoritic activity can strike the surface, similarly creating “outsourced” seismic energy. Such events are expected to give the mission scientists an inside look on Mars today, and an idea of what it was long ago.
Other instruments like the HP^3 and RISE will also be riding on InSight: the former will drill deep beneath the surface (approximately 16 feet down!) and probe the heat flowing through the planet. This will help us understand how Mars formed and out of what material. RISE will be analyzing the “nutation” of Mars, i.e. how the planet wobbles as it rotates on its axis and precesses (the circular movement of its axis of rotation - think of a top’s axis rotating around as it spins) during its orbit. This will give us an idea of how dense and large both the Martian core and mantles are - allowing us to further our understanding of planetary formation.
If you want to understand how places like Earth form and what planets in other star systems are like, it’s critical that we use the planets around us to get an idea of these universal processes.
The Telescope to End All Telescopes: How we can finally photograph another world
“Ninthly, since the famous order of the elements is seen to be vain, the nature is deduced of these sensible compound bodies which as so many animals and worlds are in that spacious field which is the air or the heaven, or the void, in which are all those worlds which contain animals and inhabitants no less than can our own earth, since those worlds have no less virtue nor a nature different from that of our earth.” - Giordono Bruno
Humanity has speculated about the heavens for ages.
For a millennia we’ve looked up and imagined the gods above, waging war during thunder and crying during the rain.
Giordano Bruno, a Renaissance astronomer and friar, looked up into the heaven in which his God lived. The thought occurred to him that the stars… rather than being pinholes in heaven, may actually be something far more shocking:
Bruno realized they were Suns. The thought drove his idea that maybe, these stars had their own planets.
Naturally, he came to think: we aren’t alone.
He was burned alive in 1600 for his heretical views.
Fast forward to today:
Kepler 438b. Gliese 667Cc. Kepler 442b.
These are exoplanets. They’re real. We’ve just discovered them in the last few years. Many of you reading this will have been alive at a time when we had not yet discovered a single one (1992).
Can you imagine that? Centuries ago a man was executed for even imagining such an incredible thing. Now, we have all lived through his dream. We know it.
The Kepler mission has found 50%+ of the exoplanets alone. Yet even this amazing telescope delivers no images, just data.
If seeing is believing, “When,” one might ask, “will I see an actual photograph of an exoplanet?”
Well, as it happens: making a telescope isn’t easy. You need to create a mirror that is bent inwards like a bowl, which can then focus an image and reflect it to a small point, through which we then can either receive it on our instrument or view it through an eyepiece.
These mirrors, are expensive and tremendously difficult to create. They need to be accurate sometimes down to the nearest atom. Precision is absolutely key.
To this effect, a technique called ion figuring exists (and was used to create the Hubble Space Telescope).
Unbelievably, the European Southern Observatory is currently constructing what will be the world’s largest optical telescope: with a mirror at 39.3 meters in diameter, the European Extremely Large Telescope will be able to directly image exoplanetary gas giants.
Even this gargantuan telescope, however, won’t give you the beautiful picture I’ve attached above.
So, back to the drawing board, you might ask, “Will we never then be able to see a photograph of an exoplanet?”
Notice I said the ESO is constructing the world’s largest optical telescope. There’s another way.
And we already have the telescope.
Einstein’s responsible (who else?) for showing us the way.
When he published his theories on general relativity, he realized that spacetime gets warped by mass. A large enough mass, he concluded, could bend space itself.
Bear with me.
When light travels across space and goes over a portion of warped space, it follows the curvature of space and it’s path of travel - its direction - is changed.
Something like a black hole, for example, might be so massive that it would alter the background of light we see around its edges. This phenomenon is known as gravitational lensing. Such a phenomenon looks like this:
What if I told you, 550 times farther from the Sun than Earth (called by astronomers “550 astronomical units”), there’s a place where this event actually happens. The Sun, as it happens, is just so massive that at this distance away (known as the gravitational focus point) our own local star so warps light that it actually bends its path into a focused point.
(Yes, astronomers, as Neil DeGrasse Tyson has pointed out, are straight up with our names (i.e. European Extremely Large Telescope, black hole etc.). We like to make them walk and talk like ducks.
Which is why I hate it when I go jogging and find a road called “Flattest Hill road” only to learn the hill’s a thousand times less flat than its name implies UGH)
So, and I did ask you to bear with me, now that I’ve told you the big secret, you probably want to know the specs: “How much detail could we see on an exoplanet’s surface?”
I hope you’re sitting down.
We could potentially resolve at a 1 km resolution.
Anything 1 kilometer and larger on the surface would be visible. That’s a little over 3000 feet in length.
What things are on Earth that you would be able to see with that resolution? A mountain. A city. The Golden Gate Bridge.
The only thing stopping us from using this natural telescope is ourselves.
(Image credit: ESO/L. Calçada and Wikimedia Commons users Urbane Legend(optimised for web use by Alain r) respectively)
NASA just shared this awesome photograph of “gravitational lensing” that I described above:
This is nicknamed the Cheshire Cat galaxy and it’s several galaxy images being warped by all the mass of dark matter in between them and us. Learn more here…
A team of astronomers just used the gravitational lensing technique from a quasar in another galaxy in order to magnify images of the stars in that galaxy.
It looks like they have just discovered, for the very first time EVER, extragalactic planets. Planets inanother galaxy! If that doesn’t make your jaw hit the floor nothing will.
The planets discovered include planets with a mass comparable to THE MOON and Jupiter. THE MOON. I am just totally geeking out right now. The galaxy is located 3.8 BILLION lightyears away!
Here’s an image from the article:
This image shows four lensed quasars (the white dots) and the lens galaxy in the center.
When I am able to get access to the actual article I will read it and probably have much more to say. In the meantime this says a tremendous amount for the sheer potential of what a gravitational lens-telescope could accomplish. Wow.
The method used to analyze the data was a statistical one. Models were built with various theoretical scenarios in order to see which produced fluctuations in the light the telescope received.
Fluctuations? Yes. Like the radial velocity method of detecting an exoplanet. Still confused? It’s okay: when a planet orbits a star, they share a common center of mass that both the star and the planet technically both orbit around. The star is often so much more massive however that it merely wobbles. The wobble causes the light of the star to fluctuate. I can go into much greater detail for those interested in this.
Back to the alleged-discovery:
The light wobbles detected from this galaxy best matched a model that indicated the presence of 2000 rogue extragalactic planets. These are planets that are orbiting between “Solar Systems” so-to-speak. Insane. Quite a claim!
