On the other hand, the short-story ending does not seem consistent with situation in The Caves of Steel. The reader might view it as a "first draft" of sorts, with ideas that were later changed. Asimov would re-shuffle ideas at times — the short story "Victory Unintentional" has a non-human civilisation on Jupiter, which is incompatible, even though the story features positronic robots obeying the Three Laws. In "Mother Earth," the latest of the Spacer worlds is Hesperus, settled from Faunus, although this is not necessarily contradictory of the history of Solaria provided in The Naked Sun — at one point in the story itself, the number of Spacer worlds is literally given as "some fifty worlds," not a firm, even fifty. The problem can be reconciled by supposing that at the period depicted in the later novels, Solaria had only recently (as in the past few centuries) been settled by mankind.
Asimov himself is ambiguous about the link, saying:
What interests me most about 'Mother Earth' is that it seems to show clear premonitions of the novels Caves of Steel and The Naked Sun, which I was to write in the 1950s." (The Early Asimov.
Earth faces a confrontation with its colonies, the "Outer Worlds." A historian looks back and sees the problem beginning a century-and-a-half earlier, when Aurora got permission to "introduce positronic robots into their community life." No date is given, but fifty years before the story starts, the Outer Worlds established an immigration quota against incoming Terran citizens. The balance of power then tipped. Now war appears likely, and there are rumors that Earth has developed an unknown weapon, code-named the "Pacific Project."
On Aurora, there is also concern, but the Aurorans decide that the threat cannot be serious. They use authoritarian methods to suppress Ion Mereanu and his Conservatives, who wish to help Earth. They then call a gathering on Hesperus, one of the Outer Worlds, to unite them against Earth.
There is some rivalry from two other planets, Rhea and Tethys. "All three planets were identically racist, identically exclusivist. Their views on Earth were similar, and completely compatible... But Aurora was the oldest of the Outer Worlds, the most advanced, the strongest militarily... Rhea and Tethys served as a focal point for those who did not recognize Auroran leadership." But Earth unexpectedly sends a threatening message to all of the worlds, uniting them against Earth.
War follows (later termed the "Three-Week War" by historians), and Earth swiftly loses. Trade is ended — the Outer Worlds have no need of Earth's exports, which are mostly agricultural. Earthmen are not allowed to journey beyond the Solar System.
We then get the explanation. The war was planned in the expectation of defeat — that was what the "Pacific Project" was all about. This is in part to force Earth to make necessary reforms, the use of robots, hydroponic agriculture, and population control. But the Outer Worlds will also weaken and split, because their worlds are biologically ill-suited to long-term human cultures. Several consequences are predicted from the entire conflict:
This fits with Asimov's wider themes, but is not easy to reconcile with the situation found in The Caves of Steel. Possibly the reforms failed, and the Spacers learned enough biology to remain healthy and united. But no later work says anything concrete about the matter.