The next upgrade is in a new section of Phendrana Drifts; in fact it covers most of the remaining exploration to be done there.
Transport to Magmoor Caverns South
Get to Transport to Magmoor Caverns South. This is near the Quarantine Cave, but perhaps the fastest route from the ship is via the Root Cave to Magmoor Caverns, then via Magmoor Workstation to the lift in Transport to Phendrana Drifts South.
There is a Spider Ball track here with a white door on top. The last time you were here you couldn't get through but now you can.
A short passage guarded by a Bombu. There is an Energy Tank visible here but you'll need to come back for it.
This is a large cylinder cut into the ground; you start at the top. There is water at the bottom and there's a good chance you will land in it if you're not careful, but it's not too hard to platform your way back up to the top again.
If you land in the water you might as well get a scan of a new creature here called the Jelzap. It's got three large fins and is able to completely separate the two halves of its body. You can't hurt it unless its halves are separated, but then you should be able to take it out with a single Charge Beam shot (any flavor). You're drawn towards it while its halves are separated and it jams your visor at the same time, so get just close enough for them to split and fire.
There are Ice Parasites patrolling some of the ledges, and Flickerbats swarming around as well. Get the Ice Parasite scan now if you missed it earlier.
Get to the bridge just below where you came in and go through the door there.
This is just a short passage serving as a shortcut to Research Core; we're just covering it here to avoid leaving holes in the map. You could, theoretically, get to the Frozen Pike via this route instead of through the Transport, but it would be a longer trip and you'd have to deal with all those Space Pirates again. This isn't the direction you want to go, so turn around and go back.
Frozen Pike (cont.)
There are two more doors further down, but you can't reach the lower one at the moment so go through the upper one. You will end up making a large loop to come back through the lower door, so don't worry about having to come back.
Frost Cave Access
You need to use Morph Ball mode to get through most of this passage. There are Ice Beetles and Scarabs near the end.
This is a large cavern with ice covered water at the bottom. A new type of Metroid, called the Hunter Metroid, is lurking near where you come in, so be prepared to get a quick scan and take it out before it does much harm. It's similar to the Metroids you've seen already but it's red and can strike from a distance. Use an Ice Beam and Missile combination which is effective against most Metroids.
You'll also see a benign creature called a Glider hovering around. You can use the Grapple Beam to catch a ride on them, when you get the Grapple Beam back that is.
There is a Missile Expansion under the ice at the bottom, but it's out of reach at the moment. If you fall and land on the ice then there is a trail of ledges leading back to the start.
From the start, look up to the ceiling and locate the two stalactites there. Fire a missile at the one on the right, then follow the ledges down to where it landed. Jump onto the stalactite and then to a ledge with a door.
Save Station C
You've been to station D already, so now you've finally found station C. This isn't an especially dangerous section so a save isn't really needed here, but it's not going to hurt.
Frost Cave (cont.)
Now fire a missile at the other stalactite and get to where it lands. Use it the same way to get to the next door.
Upper Edge Tunnel
Nothing but a Morph Ball tunnel, though the effect of the ice you're travelling through is rather pretty.
This is cylinder very similar to the Frozen Pike. Flying Pirates attack when you enter. There is much to explore in the upper half, but there isn't anything you can do about it now. Drop into the water and get to the door there.
Lower Edge Tunnel
Bombus guard this passage. It starts underwater but you surface about half way through.
This is a cavern very similar to the Frost Cave. Despite the name, there are no Hunter Metroids here, at least for the time being. Also, the water at the bottom isn't covered with ice. There are Jelzaps in the water and Flickerbats circling above it.
Locate the three stalactites on the ceiling and fire missiles to knock them down. Two land very neatly on Jelzaps with a satisfying crunch, and the third lands on a ledge near a door. The stalactites in the water act as stepping stones to reach the ledge where the third one landed, but it's a bit difficult to follow them because the Flickerbats can knock you off. (You might try thinning out the Flickerbats a bit first, but you'd be firing blind so it may not be worth it.) If you land in the water then get back to the near ledge so you start jumping the stepping stones again. Once you reach the far ledge, use the stalactite there to get to the door.
This is a short passage guarded by a Bombu. It ends under water.
This room in almost completely under water which makes getting around and seeing where you're going difficult, all the better to appreciate the upgrade you're looking for.
You start in a passage which leads to a hole with Aqua Reapers at the bottom. These are similar to the Reapers you've already met but look more like squid tentacles. There is the occasional Jelzap here as well.
Once you drop into the hole you'll find it impossible to go back, so cross to some ledges on the far side to another passage. There are some prehistoric looking frozen fish on the left side, so if you see them on your right then you're going the wrong way.
Drop down into a second hole with Aqua Reapers. Again, once you do you won't be able to get back, so scale the ledges on the far side. By now you should be able to spot what you're looking for, but if you have trouble then try switching to infrared since it glows bright yellow. Either way, you'll find the Gravity Suit in a little nook at the top of the ledges.
The Gravity Suit allows you to move and see as easily underwater as in the air.
Now that you have the Gravity Suit you should be able to get out of the second hole up to the passage with the frozen fish. You still won't be able to climb out of the first hole to the door where you came in though. Instead, jump to a ledge above the passage and then out of the water to the upper level of the room.
You might notice a Missile Expansion in a nook by the ceiling, but it's unreachable for now. There is a small pool in the corner here where you land near the entrance if you jump in. But it will be better to explore some new territory instead of backtracking. So scout around for a ramp on one side of the room which leads to the exit door.
This is a small cave guarded by a Sentry Drone.
Hunter Cave (cont.)
You're now on a ledge opposite the path you followed the first time through. Flying Pirates attack when you come in. Follow the ledge, being careful not to fall since you can't get back without going through the Gravity Chamber again, to the last door in the room.
Hunter Cave Access
This passage goes underwater where it is guarded by Jelzaps.
Frozen Pike (cont. again)
As promised, you've gone full circle back into the Frozen Pike through the door you couldn't reach earlier. You can reach the door now, should you want to, now that you have the Gravity Suit. Make your way to the surface where you will be met by Flying Pirates.
Expansions (Chozo Ruins)
There is one expansion in the Chozo Ruins you can get now with the Gravity Suit. As usual, it's a bit out of the way so you may want to postpone getting it until you're in the area anyway.
Get to the Watery Hall as you did when getting the Charge Beam. (There are now Chozo Ghosts in the Arboretum; you can either stand and fight or just go through.) You've probably been here a few times now without noticing where you might find a very well hidden item. Get to the deepest part of the water, on the opposite side of the entrance and the ledge where the Charge Beam was. There is an underwater passage here, so follow it until you come to a ledge. (This part of the room isn't marked on the map, so there is really very little in the way of hint to find this.) You wouldn't have been able to reach this ledge earlier, but with the Gravity suit you are, so jump up and collect a Missile Expansion.
Expansions (Tallon Overworld)
There is an additional Missile expansion in the Tallon Overworld you can reach now. It happens to be right on the way to the next destination so get it now.
Frigate Crash Site
Get to the Frigate Crash Site and jump into the water. Walking along the path of tree roots down there, look toward the shore on the same side as the door from the Overgrown Cavern and you should be able to spot the Missile Expansion in a nook inside a large boulder. Jump from the tree roots to reach it.