Flutter mosaic issue

main.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: ListView(
            children: [
              MosaicBlock(),
            ],
          ),
        ),
      ),
    );
  }
}

class MosaicBlock extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return AspectRatio(
      aspectRatio: 16 / 9,
      child: Row(
        children: [
          AspectRatio(
            aspectRatio: 1,
            child: Image.network(
              'https://placekitten.com/800/500',
              fit: BoxFit.cover,
            ),
          ),
          Expanded(
            child: Column(
              children: [
                Expanded(
                  child: Container(color: Colors.green),
                ),
                Expanded(
                  //child: Container(color: Colors.red),
                  child: Image.network(
                    'https://placekitten.com/600/800',
                    fit: BoxFit.cover,
                  ),
                ),
              ],
            ),
          )
        ],
      ),
    );
  }
}