The DAWN spacecraft, the one with the awesome Ion Thrusters, that has already performed an historical orbiting maneuver around the asteroid Vesta located in the asteroid belt between Mars and Jupiter, is closing in fast on the largest dwarf planet in the asteroid belt: Ceres. Back story here: https://gregole.com/2015/01/27/mission-to-the-asteroid-belt-codename-dawn/
March 6th is the day DAWN will insert itself into orbit around the weird little world that is Ceres – the closer we get, the weirder it looks.
This Feb. 19, 2015 image shows the swarf planet Ceres provided by NASA, taken by the agency’s Dawn spacecraft from a distance of nearly 29,000 miles (46,000 kilometers). It shows that the brightest spot on Ceres has a dimmer companion, which apparently lies in the same basin, seen at center of the image. Dawn is preparing to rendezvous with the largest object in the asteroid belt located between Mars and Jupiter, scheduled to go into orbit Friday, March 7 after a three-year journey. Dawn is about 590 miles (950 kilometers) in diameter. (AP Photo/NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)
Catch that? Friday March 7th? Really? They must have meant Friday March 6th… Oh well, to err is human and rocket scientists are human too! And the two bright white dots? No one has the vaguest idea. None whatsoever. Hack around NASA’s website – they are utterly surprised and clueless. No one predicted bright spots, or didn’t predict them… You can almost hear some super-brilliant post doc (when I was a little kid he (yeah it would be a guy get over it) would also have a thick accent of some sort – probably German) would say something like, “Yes, and if we see concentrated anomalous optical variegation (bright spots) it is a clear indication that….” or not. But no one even suspected they would see anything like that so our scientists are puzzled, as well they should be. Maybe we’ll find out what’s going on out there pretty soon.
This is cool video showing some great shots of Ceres. You know, we have never ever, as in never seen Ceres like this. Not even the Hubble space telescope can resolve Ceres this close and I especially like the time sequence showing photos of Ceres growing ever larger and more distinct as DAWN approaches:
Here’s another good video, and at 1:25 in, there is an excellent animation and explanation of how DAWN is going to use her Ion Propulsion Thrusters to slip into orbit around Ceres.
Oh and now the top cosmological space minds are working up to a conjecture that asteroids and dwarf planets brought water to earth since the “comets formed the oceans” conjecture is looking a bit thin! Yeah, Friday, March 7th. No, seriously, I love all these top science types and I’m grateful they are working on the big questions. Allow me though to slip in this gentle reminder: we don’t know; and just because we think we know a lot, doesn’t mean we know everything. And some of the things we know, ain’t so! But we keep learning and that’s pretty cool.
It won’t be until mid-April that DAWN will be really close to Ceres:
Over the course of this year, as the spacecraft spirals to lower and lower orbits, the view will continue to improve. In the lowest orbit, the pictures will display detail well over one hundred times finer than the RC2 pictures returned a few days ago (and shown below). Right now, however, Dawn is not getting closer to Ceres. On course and on schedule for entering orbit on March 6, Earth’s robotic ambassador is slowly separating from its destination.
“Slowly” is the key. Dawn is in the vicinity of Ceres and is not leaving. The adventurer has traveled more than 900 million miles (1.5 billion kilometers) since departing from Vesta in 2012, devoting most of the time to using its advanced ion propulsion system to reshape its orbit around the sun to match Ceres’ orbit. Now that their paths are so similar, the spacecraft is receding from the massive behemoth at the leisurely pace of about 35 mph (55 kilometers per hour), even as they race around the sun together at 38,700 mph (62,300 kilometers per hour). The probe is expertly flying an intricate course that would be the envy of any hotshot spaceship pilot. To reach its first observational orbit — a circular path from pole to pole and back at an altitude of 8,400 miles (13,500 kilometers) — Dawn is now taking advantage not only of ion propulsion but also the gravity of Ceres.
On Feb. 23, the spacecraft was at its closest to Ceres yet, only 24,000 miles (less than 39,000 kilometers), or one-tenth of the separation between Earth and the moon. Momentum will carry it farther away for a while, so as it performs the complex cosmic choreography, Dawn will not come this close to its permanent partner again for six weeks. Well before then, it will be taken firmly and forever into Ceres’ gentle gravitational hold. http://www.jpl.nasa.gov/blog/2015/2/dawns-approach-takes-shape-as-the-face-of-ceres-is-revealed
It’s an interesting concept to wrap your head around, orbiting Ceres, a comparatively large body in relation to DAWN, but relatively tiny little world compared to the solar system millions of miles across. I think us humans instinctively, or perhaps a better word is unthinkingly, think of going somewhere a problem of traveling in two dimensions – like say, going to work. We picture ourselves, at home in the morning, a place in time. Static. We get in a conveyance or convey ourselves by foot to another location, in more or less a straight line with maybe a couple of turns left and right; and in my case some lane changes on the 101 that are way, way too exciting for that time of day. But essentially, we move on the surface of a gigantic, compared to us, planet; so gigantic in fact that even though it is spherical in shape, we don’t even notice it. So when we go anywhere, we think of it as going from the proverbial point A to the projected point B.
Movies don’t help. From the earliest portrayals of space travel, Flash Gordon got in his rocket ship, and blasted off for planet Mongo and an eventual epic confrontation with the Evil Ming the Merciless:
In the comic strip, when the heroic Flash Gordon and his friends land on the fictional planet Mongo, they find it ruled by an evil Emperor, a despot who quickly becomes their enemy. He is not named at first, only being known as “the Emperor” until several issues later when his name is revealed to be Ming.
The capital of his empire is named Mingo City in his honour. In addition to his army, Ming has access to a wide variety of science fiction gadgets, ranging from rocket ships to death rays to robots. Though evil, he has his weaknesses, which include a desire to marry Flash’s beautiful companion, Dale Arden. Ming’s daughter Princess Aura is as evil as he is when the series begins, but is eventually reformed by her love for Flash, and later for Prince Barin of Arboria. http://en.wikipedia.org/wiki/Ming_the_Merciless
Kind of like going to work in the morning – get in your car and drive; or get in your rocket. It’s not that way. Space travel doesn’t work that way.
Here’s the problem. Everything’s moving when you go to another planet. All the necessary motions and maneuvers involve launching from one place that is orbiting the sun, so it’s moving in a roughly circular path, and remember it’s spinning to! Yes, the earth is spinning and orbiting. So we hurl something (in this case DAWN) off the surface of the earth, which is spinning and orbiting, into some weirdly shaped 3-dimensional path, alter that path with rocket impulses to aim the thing at…What!? Something else that is orbiting and spinning; so on one fundamental level, you are actually aiming at where you think that thing is going to be at when you want to get there, not necessarily where it is now.
Now to position DAWN so it can actually orbit Ceres, DAWN has to be set to match Ceres’s orbit around the sun – DAWN has to sort of “shadow” Ceres; and then slip in close enough to become captured by Ceres’s gravitational field. So far so good? No. There’s more. Remember that Ceres is orbiting the sun, but also spinning about its axis like any good dwarf planet would. And ideally, if fact absolutely no question about it, we want DAWN to orbit Ceres pole to pole. Why? So as DAWN makes progressive orbits around Ceres, Ceres is spinning underneath DAWN so DAWN’s ultra-cool instruments can continuously peer at new places on Ceres. Good thinking. Now if those guys could just learn to read a calendar.
Question: If earth’s oceans came from asteroids, where’d the asteroids get their water?